My favorite example of "Tu Quoque" is the following

A movie patron shuffles up to the ticket taker holding a burger bag and a large drink, the usher calmly and politely mentions, "I'm sorry, but the theater has a policy of -no-outside-food-or-drink-". The patron, in a huff, grumbles and says, "that other patron over there, who's walking into one of the movies brought in their own food!"

The usher, calmly and politely explains, "it doesn't matter if someone else is breaking the rules, I must remain at my post, so I have no ability to investigate your claim (accusation) at this particular moment in time, but I would kindly ask that you either finish your meal outside the theater or place it in the nearby bin before entering".

A very similar argument was promulgated recently in the headlines. When it was pointed out that Trump implicitly requested specific favors in exchange for pending monetary aid, instead of actually defending himself, he instead chose to attempt to distract the press (and everyone else) by suggesting that Biden (that other guy over there) "did the same thing" (Tu Quoque).

It doesn't matter if someone else committed the same crime as you "and got away with it".

That's NOT a defense. It's a RED-HERRING.