I'm not prejudiced, but...

I don't want to sound prejudiced or anything, but for one, I am not going to vote for a colored man to be our president. Russia is a nation that is very much alive. Perhaps the last truly alive people of the white race. I'm totally not a racist, I just talk this way. Any sentence that starts with the words "I'm not prejudiced, but...," or similar formations ("not racist, but" or "not homophobic", "not sexist", etc.) is likely to contradict itself very rapidly. If you are saying a sentence that starts with "I'm not X, but…", this very likely means that you are X. Unless X is something like "a lawyer" or "a scientist"; in the latter case there is a distinct possibility that the statement to follow is a denial of mainstream science (evolution, global warming, etc.).

The technical terminology for this type of statement includes "false front" and "".

Variations
Variations include ending the sentence with "not that there's anything wrong with being gay/African American/whatever" after they have just made an offensive statement about them. Or the old classic, "I'm not anti-(fill in the blank); some of my best friends are (fill in the blank)." As one editor's grandmother is fond of saying: "The Lord knows I cherish black people, but…"

Some say that they judge the conduct, not the person. For example, "I don't hate homosexuals, but I can't approve of their conduct." When people ask them "Doesn't your view of homosexuality encourage prejudice against gays? Isn't this homophobic?" they can say "Not at all. I reject homosexual conduct, not people." This way, they think that they can eat the cake even though they do not really have it: they can discriminate against gays and claim at the same time that they aren't homophobic. It's good to notice that this can be varied to justify racism: "Oh, I have nothing against the black people, but their behaviors, like the fact that they choose to live in this continent. I am not a racist or anything like that" or any other form of discrimination.

There's also the misanthropic (read avoidant), "I'm not prejudiced, I hate/fear everybody equally!"; the paranoid "I'm not prejudiced, everybody’s out to get me over something or other.”; the schizoid "I'm not prejudiced, I have (almost) no interest in or attachment to any social relationships.”, the schizotypal "I'm not prejudiced, I just believe/do something that perplexes you.”, the antisocial-borderline-histrionic/narcissistic, "I'm not prejudiced, nobody’s (words/actions/rights) matter to me anyway.” and the obsessive-compulsive "I'm not prejudiced, I just micro-manage my thoughts.” Or, putting it ironically, "I'm not prejudiced, (I just have no idea why) they seem to hate me.”

Why people say this
These words are often spoken in the mistaken belief that simply saying "I'm not prejudiced" is enough to exempt the speaker from responsibility for the offensive comment they are about to make. In this context, the "I'm not prejudiced" statement is an example of argument by assertion, although it's sometimes backed up by non sequitur statements such as "I like curry" or "I enjoy the music of Queen and the Pet Shop Boys," to demonstrate just how unprejudiced the speaker is.

The increasing prevalence of these kinds of statements demonstrates one of the more annoying effects of political correctness, in that people with controversial opinions are more concerned about others thinking that they are racist or otherwise discriminatory than scrutinizing the actual content of their real beliefs and statements. "I'm not prejudiced but…" is a plea for acceptance from others, not an attempt to be more accepting and self-aware in good faith. Thus, this genre of false-front statements reveals that the speaker is more afraid to be branded as racist or otherwise prejudiced than to even acknowledge to themselves their own prejudices.

If you have doubts as to the appropriateness of your words or beliefs or if you think they may marginalize others, the appropriate course of action is to scrutinize them and then if they are harmful, not express those things. Even if one ends up making a mistake, one good apology and a sincere and sustained effort to self-check and change one's outlook is more appreciated than any awkwardly non-sensical assertions of "I have a black friend" or "I'm not a bigot but… please overlook that I really want to say something that harmfully generalizes women/disabled people/people of varying gender and/or sexuality and/or ethnicity."

An Alternative Reason
It may also be possible that the person intellectually understands that bigotry is bad, but genuinely fails to realize that what they are about to say would indeed qualify as bigotry. For example, it is a known fact that, on average, women have less upper body strength than men. To suggest that it would still be sexist to point this out would be to take an Orwellian approach to information (although any conclusions you might extrapolate from this fact could potentially be quite sexist indeed). Thus, to say "I'm not sexist, but women on average will not be able to bench press as much as men." would be a true and completely non-contradictory statement. So if someone is under the impression that, for example, women are also statistically less intelligent than men on average (they are not), then they would likely think that acknowledging said (non-)fact would also not be sexist.

People who aren't prejudiced, but…
Organizations which are undoubtedly racist have attempted to improve their image with the same kind of rhetoric. For example, in a policy statement for the far-right British National Party, leader Nick Griffin repeatedly stated that the party is "not racist", while laying out his vision for an all-white Britain and his belief that nationality is defined along blood lines rather than residency or even cultural factors.