Biphobia

Biphobia is a hatred or irrational fear of bisexuality, or the specifically bisexual parts of self-identified, well, bisexuals. Though it is very easy to conflate with homophobia, the two are separate things with specific definitions. Notably, biphobia is a distinct prejudice from homophobia and is often found within the LGBT community, and contributes to bisexuals feeling unwelcome in certain sections of it. That being said this does not mean that bisexual people are never subject to homophobia — as often bisexual people are subject to the intersections of homophobia and stereotypes unique to bisexual people.

Overlap with other sexuality phobias
Biphobia overlaps with, but is distinct from, homophobia. Hatred towards bisexuals from certain types of people, groups and outlooks mostly centers on the fact that they are attracted (whether sexually or romantically) to people of the same sex, which is a form of homophobia. Biphobia refers specifically to feelings toward people who are attracted to the same and differing sexes and has common ground with objections to pansexual people (who may also identify as bisexual in some contexts). It is possible to be homophobic but not biphobic (e.g. if one prioritizes interest in the opposite sex) or biphobic but not homophobic (e.g. if one believes that bisexuality is “unnatural” or spreads disease).

The implications associated with biphobia vary by social group. Heterosexuals may deny biphobia's existence on the basis that heterosexuality is the social norm and bisexual individuals are expected to either 'come around' eventually, or remain available as part of fetishistic fixation (examples include men who fantasize about 'lesbians' that will go down on them, or women who are enamored with the idea of men having sex with one another), not expressing any identity or agency outside of the demands of heterosexual voyeurs. Biphobia can also come from within the LGBT community (usually homosexuals), with implications of betrayal or untrustworthiness. This often centers around the idea that bisexuals could discard the community and all of their social stigma simply by 'going stealth'; biphobia from this sector will often carry phrases such as 'straight passing', and subtle feelings of jealousy or betrayal. Finally, those who interpret bisexuality as reinforcing the gender binary (tacitly defining bisexuality as 'attraction to two genders, as opposed to an indifference to, or nuanced attraction to, the binary genders) will sometimes express the sentiment that bisexuals are trans-exclusionary, and thus transphobic.

Rationalizations and common stereotypes
Like homophobes and transphobes, biphobes use various arguments against their chosen group. Whereas homophobic arguments have the end goal of preventing gays and transgender people from being given equal rights, biphobic arguments are more about spreading distrust and stigmatization of bisexuals.

"Bisexuals are promiscuous"
There’s not actually much reason to think that being lesbian/gay vs. bisexual vs. straight makes a big difference in promiscuity. But many keep perpetuating this myth, and the same counterpoint applies: some bisexual people are promiscuous, but so are some homosexual and heterosexual people, and individuals from each group are also interested in committed, monogamous relationships. Beyond that, someone exploring their sexuality is not necessarily promiscuous. Also, this “attack” assumes that promiscuity is inherently bad.

"Bisexuals sleep with the enemy"
This bizarre 'argument' tends to come from gay, lesbian, or trans persons, and is usually either a form of emotional revulsion (comparable to homophobes trying to make a point against two men having sex by talking about anal sex being gross to them) or a commentary on bisexuals giving support to a heteronormative society. One person saying this is the political lesbian Julie Bindel, who has written "I believe now, that if bisexual women had an ounce of sexual politics, they would stop sleeping with men." This fails simply because one shouldn't judge others for their choice in partners, and neither homosexuals nor heterosexuals are 'the enemy'. One's love life should be based around self-fulfillment and sharing it, not a political statement.

"Bisexuals will give you AIDS"
A 1989 issue of Cosmopolitan and a similar 1991 article in the New Women infamously spread the idea that women should not date bisexual men as they would be the "untrustworthy conduits" to spreading HIV into straight communities given the assumption they regularly have unsafe sex with other men. This harmful stereotype is used as justification by straight women to refuse to date bisexual men, and given the existing prejudice that some gay men have for bisexual men this leads to discrimination in dating and limited access to social support from romantic/sexual partners for bisexual men. This stereotype feeds into the above mentioned stereotypes of "bisexuals sleep with the enemy" (gay men with AIDS) and "bisexuals are promiscuous" (they regularly have casual unsafe sex).

"Bisexuals are just greedy / horny"
Some people just see this argument as a joke (even among bisexuals), but in the event that it's supposed to be taken seriously, it's more than likely a result of jealousy, as bisexuals (on paper) have a larger pool of potential partners. It also carries the implication that people choose to be bisexual because they are greedy, when homosexuals are routinely accused, with next to no evidence, of choosing their sexuality (with the same rebuttals, that sexuality cannot be chosen, applying to both cases). The "horny" accusation is similar to what homophobes say about gay people, that they are attracted to all people of the same sex. Likewise, even though there's probably someone out there who enjoys it, being stereotyped and insulted is a turn-off for bi people.

"Bisexuals are just experimenting"
'Just experimenting' is a part of exploring one's sexuality. Most awkwardness and apprehension that bisexuals feel when 'trying things out' is due to A) society's perceptions of sexuality, B) the notion of hurting someone they've experimented with if it doesn't work out C) fear of rejection, and D) being uncomfortable with continuing to learn things about themselves. People explore their sexuality naturally throughout their lives, and someone being true to oneself, finding what makes them happy and the kind of people they in turn can make happy should not be discouraged.

"Bisexuality does not exist"
This is known as 'bi erasure'. It can take different forms, but usually consists of minimising the presence of bisexuals by identifying them as something else, be it gay, straight, greedy, or confused. There is also a tacit form of bi erasure in media wherein characters shown to be attracted to both sexes will, when pressed on the issue, claim that they 'don't like labels', or something similar, and refuse to elaborate. This gives the impression that the concept of bisexuality is acceptable in mass media, but the word is not. The concept of sexual fluidity has been widely documented, particularly in women,  and the well-known Kinsey scale has stood the test of time.

Many people seem to struggle with accepting that somebody could be sexually attracted to more than one gender, insisting instead that they must really have a preference for one or the other. Aside from being an argument from incredulity, this misses the point that bisexuals don't necessarily have to be equally attracted to both genders (a 3 on the Kinsey scale) — some are, while others may have a general preference for either men or women, but as long as they are sexually attracted to and/or willing to have sex with both, they remain bisexual by definition. Bisexuality includes at least points 2 to 4 on the Kinsey scale, and arguably positions 1 and 5 as well (people who are basically heterosexual with some latent homosexual tendencies, and their gay counterparts with some hetero tendencies).

The misconception of self-identified bisexuals being just "confused" falls into the following two paradoxical categories:

"Lots of bisexuals are just closeted gays"
There is a very mild degree of truth to this. Yes, some gay people, on the path to coming out to themselves, will identify as bisexuals. One of Dan Savage's favourite talking points, this line of thinking ignores the many gay people who never identified as anything other than gay.

Many people in this situation may very well be actually bisexual, and for those that identify as bisexual during a phase as they realize they are gay, it is extremely bad etiquette to out someone to themselves without caution when they are not ready. For some, it is part of their coming out process, and may do it for their own social survival (or in some extreme cases, literal survival) in a homophobic area. What people in this process need is compassion and support, not distrust spread about them in a community they are supposed to feel safe in. Also some people identify as lesbian/gay when they get their first same sex crush/lover and then end up identifying as bi later on if they discover their feelings for the opposite sex were not insincere. It goes all the ways.

"Lots of bisexuals end up in opposite sex relationships"
On the other hand, some biphobes may point out that a lot of 'bisexuals' will cease having same-sex relationships and gravitate towards opposite-sex ones as they get older. Aside from being mostly anecdotal evidence, this method of smearing bisexual people does not look at the reasons why this trend happens. Even though by and large bisexuals lean towards attraction to one sex rather than an other, some who preferred same-sex relationships move towards opposite-sex ones in later life due to social factors, simply finding true love with a person of the opposite sex, or marrying for another reason (such as an unexpected pregnancy, which is less-than-likely to occur in a gay relationship).

Prejudice and bigotry towards gay people makes some bisexuals want to appear heterosexual to the outside world for their own well-being. As thoughts turn to family life, they may feel immense pressure from their own family (alongside society at large) to conform to heterosexual marriage (even before you consider that same-sex marriage or its denigrated equivalent the civil union may be illegal or not accepted where they live) and have children through bog-standard sexual reproduction instead of same-sex adoption or surrogacy, both for the way they themselves would be viewed and the risk of their offspring being bullied for having same-sex parents. This is especially true if they are an only child, and so more likely to be pressured into continuing the family line.

It is society that makes same-sex relationships less accepted, and this problem will slowly become less and less widespread as society inevitably progresses towards greater gay acceptance. In addition, homosexuals who spread these ideas about bisexuals in the LGBT community make said bisexuals even less likely to engage in same-sex relationships.

There's also the fact that there are simply more straight people in the world than people who are not straight, so one's same-sex dating pool is always going to be smaller than one's opposite-sex dating pool. This accusation is also sometimes thrown at heterosexual persons who experimented with same-sex relationships before deciding they were completely straight - an outcome of sexual experimentation that is just as likely as any other. This then falls flat for the simple fact that the person is not bisexual in the first place.

Poverty rates
Gay men as a demographic in the United States have a poverty rate about 12%, with lesbians at 18%; all the while bisexual people experience higher rates of poverty with bisexual men obtaining a poverty rate of 20% while bisexual women unfortunately obtain a poverty rate at a whopping 30%. Transgender people regardless of sexual orientation also experience similar poverty rates to bisexual women Explanations for such rates often appeal to the lack of safe spaces and lack of inclusivity for the B's and T's in the LGBTQ+ community -- something contributed in part by biphobia and transphobia within the queer community.

Intimate partner violence
37% of bisexual men experience intimate partner violence, compared to the 29% of straight men and 26% of gay men. For bisexual women the rate is as high as 61%, with lesbians experiencing a 44% rate, and straight women a 35% rate It been argued that the above mentioned stereotype of bisexual people being more promiscuous has fueled rationalization in some that they are more likely to be receptive to sexual coercion.