Whataboutism actually does have a formal meaning, though that's gotten lost over the fact that it's been happening so rampantly:
"Whataboutism (also known as whataboutery) is a variant of the tu quoque logical fallacy that attempts to discredit an opponent's position by charging them with hypocrisy without directly refuting or disproving their argument, which in the United States is particularly associated with Soviet and Russian propaganda."
https://en.wikipedia.org/wiki/Whataboutism
To expand on this, there's a few problems, logically speaking, with whataboutism:
1)The "hypocrisy" is always assumed and never supported.
So I say, "Trump is a bad person for raping a school bus full of children!" and the Trump supporter comes back with, "Whatabout when
Clinton raped a school bus full of children? The hypocrisy is deafening!"
Well, that begs the question: whose hypocrisy? Mine? Hypocrisy has a definition: saying one thing while doing another. Did I ever defend Clinton raping a school bus full of children? If not, then where is the hypocrisy charge coming from?
2)As the Wiki definition already points out, the whataboutism doesn't even directly refute the argument.
So I say, "Trump is a bad person for raping a school bus full of children!" and the Trump supporter comes back with, "Whatabout when
Clinton raped a school bus full of children?"
Which begs the question: so what? Does that mean it's a rape free-for-all now? Can I now rob my neighbor's home because some other guy robbed another person's home? The premise that because a previous person did something bad that it's okay for the current guy to do something bad is preposterous and would lead to a complete breakdown in society. So while it may feel good to argue on an internet forum, it's not something that could ever be practiced in the real world because that would quite literally result in the collapse of civilization.
3)In practice, the whataboutism nearly always fails in its attempt to draw an equivalency.
So I say, "Trump is a bad person for deliberately making a hobby of running over dogs with his car." And the Trump supporter comes back with, "Well, whatabout the time Obama hit a dog with his car when he was in college!"
This is the most common manifestation of whataboutism I see here: the implication that the common practice of a negative behavior is equivalent to the incidental negative action. And you know who that always benefits? You got it: the person who carries out the negative behavior as a matter of habit because he's now "equivalent" to the good person who did a bad thing once (and maybe not even on purpose). If this argument technique were practiced in real world terms, it would, like the previous example, lead to a breakdown in society because at that point concepts like right and wrong no longer exist.
4)And let's be serious. We're all adults here. We know perfectly well that the only reason for that practice of whataboutism, as defined by Wiki, is nothing more than to change the discussion at any cost.