I don't think it's right, either. However, it might have to do with evidence: in any such case, the evidence that he had sex with her is physical, while the evidence that she agreed isn't (in the absence of witnesses or a recording).
Maybe a man should try claiming that he was too drunk to consent, so the woman raped him.
Ok, my wife is right on this one. A man can still have sex with a woman if she’s semi-conscious or even unconscious. The same doesn’t hold true for men, if we’re that drunk... I guess physiological differences could come into play here.