Yes a man can be raped by a woman. Our bodies respond in ways that we have no control over and so it could be the same for a man. It has been known for a woman to have an orgasm whilst being raped....does that means she is enjoying it, I don't think so, it was just her body betraying her at the moment when she needed it not to. So in the same circumstances a man could become aroused even if his brain is screaming no. Unfortunately I feel men would be very reluctant to report for fear of not being believed in the same way they would be less likely to report a violent partner because men are meant to be the stronger sex.