Let me show you part of the problem. This is from the CDC.
Wow, reading that would make it seem like rape to men almost never happens right? It clearly says that the sample of men were too small to to produce anything useful. But wait, what is the very next part of that report?
Wait...what? The first part said that men reported being raped so infrequently that it was not a meaningful measurement. Then, the next part says that when you include the other things, the rate goes to 5.5 and 5.1%
Well, that is because women are raped more then men, but men have other forms of sexual violence. But wait, did I read that other part right?
What the fuck? How is a man sticking his dick in a woman who does not consent rape, but a woman forcing a man's dick into her not rape?
So, its correct to say that men represent the majority of attackers. But, sexual assault happens to men and women.
http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6308a1.htm
That is from the CDC study from 2011.