'tu quoque' am I iwrong?

[Angrboda]

Tu quoque is just a special case of ad hominem, and ad hominem is a non sequitur because nothing about the proponent of a claim effects the logical validity of the claim unless the claim is in some way dependent on a quality of the advocate. (E.g. "As an expert in biology, I can tell you that mammals didn't evolve into whales." "You have focused your studies and professional work almost exclusively on arthropods; you are not an expert in the relevant area.")

And as to the specific fallacy of tu quoque, nothing about the opposing advocate is relevant, as the opposing advocate's claim's only relevant criteria is whether it is true or not; nothing about the opposing advocate can effect the soundness of a claim about someone else, only the claim's falsehood can do that.

Oh, and I think you've got an extra i, pad.