In the OP he says it requires three elements.It seems clear to me that Cavemonster is protesting against the notion that two wrongs can "even out", assuming that they are done to opposite parties.
* A tu quoque,
* As if that's not enough, it doesn't address past behavior, but predicted behavior, becoming a.. what, premeptive tu quoque?
* The behavioral prediction itself is widely off the mark and without evidence.
He quite clearly states that is a tu quoque, not a matter of two wrongs don't make a right. The Wiki short definition is pretty good. It reads, "the argument states that a certain position is false or wrong and/or should be disregarded because its proponent fails to act consistently in accordance with that position." His example is not a tu quoque.
Is it then a two wrongs don't make a right? That argument has some merit if we assume it to mean, "occurs when it is assumed that if one wrong is committed, another wrong will cancel it out." It sounds like he is asking what you call a two wrongs don't make a right when the second wrong has yet to occur and is not even likely to occur. In order to make that argument, you have to throw out tu quoque as an element and insert two wrongs don't make a right by assuming this is what is shown in the example.
I am challenging whether the example even demonstrates that. There are other interpretations of this example of an alleged "logical fallacy" that are not logical fallacies, so it's not unequivocal. He could have started from the Wiki example:
Speaker A: President Williams lied in his testimony to Congress. He should not do that.
Speaker B: But you are ignoring the fact that President Roberts lied in his Congressional testimony!
New Version:
Speaker B: But President Elect Roberts will lie in his Congressional testimony when he gets the chance.
If you want to give that a name, call it "a present wrong and a future wrong don't make a right."
When it comes to the example in question, it wasn't set up very well. We don't know what Speaker A said other than, "I was pretty incensed that the punishment was doled out to only the boys." There are several interpretations of what might have been said to elicit the response in question, and we cannot call it a logical fallacy until we know for sure what it is. Since no tu quoque was involved yet CM said it was a critical element, it's only natural to question what was actually on the table.
You have no evidence of that.This really isn't helping the conversation at all.