"Tu quoque" is the Latin name for "you also", an informal logical fallacy otherwise known as "appeal to hypocrisy".
I pointed out that Adam Jensen is clearly just being partisan and that his arguments are irrational. It's okay when "his party" does it, because everything they do is just and good. It's not okay when "the enemy" does it because everything they do is wrong and evil. He has no justification for any of that, but that's his stance.
And when I call him out on the senseless partisanship on display, he attempts to change the subject of the conversation by pointing at my post history. He's trying to distract from the main point and imply that my argument should be invalid, not based on the merits, but because of my opinions about election fraud.