It's not something that a predator is going to advertise. I've only known one person that I thought was a rapists, and not from any direct admission but just because of the attitude towards women he had. If he wasn't a rapist it was probably just due to lack of opportunity. The statistics suggest that I've known far more that I just didn't know were. Perhaps there are certain circles where men freely admit to sexual assault, but none that I've ever been in.
Some segments of feminism just seem to take the idea of "rape culture" to its extreme. Certainly attitudes that blame women for rape are wrong. Certainly media that portrays rape as acceptable behavior are wrong. However, the idea that pretty much every aspect of culture is driving rape is a concept that is a bit harder to grasp and I'm just not sure they can connect the dots. The idea that certain feminists have that things like porn and language encourages rape just haven't proved true.
I think if people really want to reduce the incidence of rape, a good place to start would be to put effort into figuring out why the rates of rape went down in the first place. I'm pretty sure it wasn't because media got less vulgar or sexualized, yet you still have those who claim that is the miracle cure. I'm just not sure how productive that is.