I still suspect that the reason for rapeing women is in some cases to get sex easilly.
I'm very sorry, Übs, but I have to correct you on this one. I've read several books about serial killers, and most of them usually rape their victims. But that was never for getting sex easily, but to be able to completely dominate their victim. Those serial killers only want complete control and want to show their victims that they are in charge. Some of them even raped their victim after they had killed her/him. That is called Necrophilia. I hope I wrote it correct in English?
The same reason why in the WW2 the nazi's ordered their Jewish prisoners to get undressed in front of them, it's a way of showing the victims that they were the boss and your faith was completely in their hands.
Rapists are also men that like a woman that struggles against it. They get turned on by it, by their screams, the fear in their eyes, stuff like that. But it's almost never because of wanting just sex.