(Written 21 November 2018. Edits added.)
What's with all the contemporary noise about 'whataboutism'?
Example 1. A lefty complains, "Trump is a liar!" A conservative responds, "What about Hillary and Bill and Obama? Are they not liars too?"
Example 2. A pro-lifer argues that killing the prenatal is immoral and meets with the response, "What about all of the 'pro-lifers' who bomb abortion clinics, terrorize clinic staff, and block women’s legal access into such clinics?”
On one way of looking at it, 'whataboutism' is just the ad hominem tu quoque fallacy. It's old wine in a new but very ugly bottle. If the question is whether Trump is a liar, then it is irrelevant to bring in Hillary and Bill and Obama, despite their being egregious and proven liars. Similarly in the abortion case. The violence of a few pro-lifers is simply irrelevant to the question of the moral permissibility of abortion. Or suppose my doctor, who has cancer, diagnoses cancer in me. It would be absurd for me to protest the diagnosis on the ground that the sawbones has it too. What about you, doc?
So can anything good be said about 'whataboutism'?
Let's think a bit deeper about example 1. If a lefty points out Trump's undeniable flaws in an effort to show that he is unfit for office, then it is relevant to bring up Hillary's also undeniable flaws. For if her considerable flaws do not count against her fitness for high office, why should Trump's against his?
Understood in this way, 'whataboutism' is not the fallacy of ad hominem tu quoque, but a legitimate charge of double standard. Trump is being held to a higher standard than Hillary.
If the question is simply about Trump's character, then Hillary's is irrelevant. But if the two are competing for the same office, and Trump's defects are cited as disqualifying, then it is relevant to bring up Hillary's. Not to do so would be to employ a double standard.
One conclusion, I think, is that 'whataboutism' is a waste basket term that ought to be dumped. We already have 'tu quoque fallacy' and 'double standard.'
Besides, it is a barbarism.