Why does our society expect men to be raging maniacs who can't control themselves?

In our society, women are taught to be careful around men. If a woman gets raped, it’s her fault for tempting the men around her or becoming incapacitated around men. This seems to me to be an example of sexism not completely against women. In fact, I think it speaks more to our society’s low regard for the self control of men. I have often found that men have the same kind of self control as women. That is to say, some have none, some have a little, some have a lot, and some have it in spades. So my question to fluther is this: Why do we think men as a whole have no self control?