it *is* illegal to have sex with someone who is visibly intoxicated to the point that they cannot make a reasonable decision.
What happens when BOTH people involved are visibly intoxicated to the point that they cannot make a reasonable decision? In that situation, who raped whom? That is the problem with counting it as rape when a woman went to a college party, had too much to drink and had sex with a guy she met at the party. Chances are good that the guy had too much to drink as well. So, when doing statistics on rape, if the woman feels that she was not raped in that situation one might want to accept her opinion unless you have more information than just that she was too drunk to legally consent. Perhaps, the woman was the sexual aggressor and convinced the (drunk) man to have sex? Perhaps the woman went to the party intending to have sex with the man she ended up having sex with? There are many reasons why a woman would not consider sex in that situation to be rape. Is it not sexist to assume that she does not know whether or not it was rape? Especially when we assume that the man, who was also drunk, was not raped because he wanted to have sex.
PLEASE NOTE: This is not a defense of any man who uses alcohol (or any other substance which reduces the ability to make rational decisions) to engage in sex with a woman who would otherwise turn him down.