Male rape is highly stigmatized, my uncle was raped and never reported it. Reported != Actual.
Incidentally, this (even assuming reliable victimization stats that weren't distorted by it) is one of the reasons why I wouldn't assume that the threat was necessarily less serious issued against a male based simply on victimization stats indicating that women were more likely to be victimized.
http://betweenletters.quora.com/More-Men-Are-Raped-In-the-US...