I get what you mean - in any particular case it might not be possible to ever prove that the murder was actually morally justified, so maybe we’re just giving some batshit crazy stab-happy lady a pass for no reason. Still, even if we can’t know whether or not it was morally justified, we can and do know that the conditions that would justify it were common enough that I’m personally comfortable with the odds ¯\_(ツ)_/¯