Not as bad as

If you can't complain about X just because there exists another problem, Y, that's worse than X, then the only person who has any right to complain at all is the person who objectively has it worst in every way possible. The other 7 billion people's problems are meaningless by this reasoning.

The "not as bad as" fallacy, also known as the fallacy of relative privation, asserts that:
 * 1) If something is worse than the problem currently being discussed, then
 * 2) The problem currently being discussed isn't that important at all.
 * 3) In order for the statement "A is not as bad as B," to suggest a fallacy there must be a fallacious conclusion such as: ignore A.

In other words: nothing matters if it's not literally the worst thing happening. It's popular with people who know perfectly well they're doing something wrong. Since they are fully aware that they're doing something wrong, they feel compelled to attempt to justify it and do so by pointing to other (usually worse) actions.

This fallacy is a form of the moral equivalence fallacy.

Forms
There are a few different reasons someone will want to pull a "not as bad as" comparison. Consider a generic argument about something, A, and the reasoning below:

This is the most blatantly fallacious form of the argument and is a hindsight version of the "not as bad as" argument that states past actions can legitimise current actions. The existence of a worse atrocity in the past, however, does not actually justify anything — it merely points out that there have been similar things in the past. People who use this as a justification may be well aware that it's logically fallacious, and use it purely as rhetoric, or as a distraction.

Examples
Holocaust deniers and apologists use this quite frequently: "the Holocaust was bad, but Stalin killed more", ignoring the Axis's willingness to encourage World War II and is irrelevant if discussing murders carried out under Hitler's regime. Similarly, "Internet censorship in the US isn't as bad as internet censorship in China" is true, but not relevant to discussing the erosion of free speech in a country that holds free speech to be an important part of human rights. It is irrational to set the bar of what makes something wrong at the worst possible atrocity, as doing so would justify all other actions except the one that is judged to be the worst at any given moment.

It is also used occasionally as a particularly underhanded emotional appeal, in an attempt to guilt trip someone, in order to have them stop voicing a complaint. For example: "Kids of the past had it way harder than modern kids, so modern kids should shut up!!" (When I was your age…)

Sometimes valid

 * Action B is worse than action A.
 * Therefore action A is the right thing to do.

This is perhaps the most valid comparison that can be drawn if discussing two courses of action that can be taken, but like most "not as bad as" arguments potentially suffers from the fallacies of the false dichotomy and argument from adverse consequences. If the argument is about ranking things from bad to worse then it's fine; but you cannot justify A by citing only B because the two may not have anything to do with each other. This is common if secret option C is actually the best, but someone wants to make a red herring to avoid anyone spotting its existence.


 * B happens more frequently, is more dangerous, or causes more harm than A.
 * Therefore A can be ignored.

This form crops up often when discussing discrimination, but seriously falls into the false dichotomy trap by implying that one can only focus their attention on A or B and is incapable of expressing moral outrage over both.

A similar form appeals to allocation of scarce resources, such as money, time, or attention, to give the best "bang-for-your-buck":
 * We have a finite budget that we can use to fix either A or B.
 * A is not as bad as B.
 * Therefore, we should fix B.

Setting priorities for limited resources is often a valid pragmatic argument, even if it doesn't morally absolve A of any wrongs.


 * A is a better option because its only alternative is B, which is worse.
 * Therefore we must keep A.

This is a pragmatic argument if the alternative, B, really does pose a real threat, and there is no secret option C. Would assassinating a dictator in some random country create a power-vacuum that plunges the entire region into war? Then we best put up with the bastard for now!

It's also a common pro-choice argument; a legal abortion in a medical clinic is statistically the safer option compared to a back alley with some bleach and a coat hanger. So even if you believe abortion is always morally wrong, providing legal access to safe abortions is preferable to women risking their lives by having unsafe abortions.

Whether these latter forms of the "not as bad as" argument are fallacious comes down to the use of a false dichotomy and whether moral justification is sought exclusively through this argument.

Caveat
While this fallacy is certainly one to be argued against, the rational arguer should be cautious in doing so in cases where X and Y lie on a recognisable continuum. Taken too far in such a case, efforts against this fallacy ("X is not as bad as Y") may readily lead an arguer into a continuum fallacy ("X and Y fall on a continuum, therefore X is indistinguishable from, or equally bad to, Y). To avoid this, the arguer must be sure to argue against the conclusion drawn from the difference between X and Y, and not against the claim of difference itself (unless there is some rational basis for arguing that the difference truly does not exist).

Other examples

 * Stalin apologists will commonly use this logic, saying "Stalin wasn't as bad as Hitler" and will use this to ignore or deny Stalin's own genocides and crimes or even justify them in some cases. He was also not as bad as the Tsar!
 * Men's rights activists frequently try to downplay the Western world's own issues with sexism and misogyny by comparing it to conditions in the Middle East. This can go from lazy and dishonest comparisons to open Islamophobia, white supremacy, and xenophobia very quickly.
 * "Women are stereotyped by the media, but it isn't as big of a problem as poverty, wars, or human rights in the world!" (See Bjorn Lomborg for a similar one on global warming.)
 * "Yes, the US is keeping secret prisons, but we're not as bad as Saddam Hussein!"
 * "Sure, US forces tortured people in Afghanistan, but it's not as bad as what the Japanese did in WWII."
 * "Catholic priests may rape children, but what about all the bad things Stalin did?"
 * "Barack Obama might be detaining people without trial and bombing civilians in other countries, but Bush did far worse."
 * John McCain's "Sure, Americans are 'war-weary' but what about the 'war-weariness' of Syrians?"
 * "Smoking may be a bad thing, but it's not as bad as global warming/car exhausts/body odor/etc."
 * "Sure, many developed countries may still have homelessness, but at least here they have bridges to sleep under and garbage cans to eat out of!"
 * Sure, institutional discrimination against non-Christians exists in European countries with an established religion, but it's not as bad as Saudi Arabia; besides, look at those freaks in the megachurches in the US!
 * Gun rights advocates sometimes argue that gun ownership shouldn't be restricted, because people driving cars cause more deaths than people using guns and we're not restricted from owning cars.
 * Sam Harris has said that obtaining information through torture is less immoral than killing innocents as collateral damage, so in any scenario where torture could prevent the need for collateral damage, torture is the less unethical thing to do. This is a valid use of the argument, though it ignores all practical considerations about the efficacy of torture (or lack thereof). He has also said that allowing secular tyrants like Saddam Hussein to oppress their populace is a better alternative than allowing populist theocrats like Daesh to rise to power.
 * "Bashar al-Assad may be a brutal tyrant, but at least he's not as bad as Daesh!"
 * "American slavery may have been bad, but the Arabs did worse!"
 * Some naturopaths and promoters of integrative medicine level criticisms against conventional medical research and practices, claiming that the skepticism of CAM is therefore misguided, hypocritical, and/or ideological. However, as Ben Goldacre succinctly puts it, "flaws in aircraft design do not prove the existence of
 * "RationalWiki may have just stepped on your personal toe, but it's not as bad as Conservapedia!"
 * Bush was not as bad as Donald Trump.
 * Donald Trump fans often claim that Trump is not as bad as Obama.
 * When police want to speak to someone about a minor offence, the response is often along the lines of “shouldn’t you be catching real criminals?”, as if their offense is not worth bothering about just because others commit worse offenses. And that itself is not as bad as the people who just shout "ACAB" at them…