This is the same argument that's frequently used against victims of rape and other sorts of assault - used to deny them justice, on no better grounds than that their own past behavior has been merely human, and thus fallen short of whatever arbitrarily absurd standard of impossible purity that unsympathetic interlocutors choose to establish - and to re-establish, as often as necessary, in order to make absolutely certain that the standard cannot be met.

I wouldn't find that a terribly comfortable place to stand. That you seem to find it congenial gives me to wonder about the quality of your own character. Ordinarily, of course, such doubts would be unworthy of this sort of discussion. But since you've found it meet to broach the subject, why shouldn't we start the inspection of character with you? Clearly you feel yourself above reproach in this regard, so I'm not sure what reason you could possibly have to demur, when I require that you prove, to my satisfaction, your standing to argue as you do on this subject.