This sarcastic approach is a pushback that etiquette simply cannot give.
I see it not as pushing back against it, but as capitulating to it, as allowing the abuser to have the abuses justified by the acquiescence of the abused.
To abandon etiquette, decorum and civility merely as a reaction to the intensity of the challenge, is to suggest there was never any genuine commitment to them in the first place, and to indicate a failure to recognize why they exist at all: the whole purpose of acting civilized, is to contribute to civilization. It makes no sense at all, just because some choose to abandon civilized conduct, to simply jump in to the chaos with both feet and then say lamely that “they started it.” This is not the thinking of the civilized adult, but rather that of the put-upon and ill-brought-up adolescent.
I’ll have none of it. Etiquette is more essential now than ever. And within its self-enforced boundaries, is no lack of ways to make a contradictory point or refute an unreasonable challenge. It is art, not science, and it is a code of conduct, not a convenient gimmick to be used only when not faced with what is outrageous. Abandon it now, and I daresay you have little chance of ever getting it back as a means of everyday interaction, whether it is reliably reciprocal for the moment or not.