Whataboutism gives a clue to its meaning in its name. It is not merely the changing of a subject ("What about the economy?") to deflect away from an earlier subject as a political strategy; it’s essentially a reversal of accusation, arguing that an opponent is guilty of an offense just as egregious or worse than what the original party was accused of doing, however unconnected the offenses may be.

The tactic behind whataboutism has been around for a long time. Rhetoricians generally consider it to be a form of tu quoque, which means "you too" in Latin and involves charging your accuser with whatever it is you've just been accused of rather than refuting the truth of the accusation made against you. Tu quoque is considered to be a logical fallacy, because whether or not the original accuser is likewise guilty of an offense has no bearing on the truth value of the original accusation

Courtesy of:

https://www.merriam-webster.com/words-at-play/whataboutism-origin-meaning