First of all we should be fair.
Chi, you can't on the one hand reject one generalization (all women don't want to be raped) and at the same time make another one yourself (all who fantasize about rape do want it to some degree). If I misunderstood your statement feel free to correct me.
In my opinion the difference between fantasy and reality is exactly what you don't like about possible live role-plays: The knowledge and security of the victim(s) that you can stop it at any time because after all it's only a simulation, a consensual sex game. Both partners involved (more eventually) always now it's all safe and sound and everyone can stop it at any given moment if they feel uncomfortable.
That is the fun most people have when doing a role-play ... the rape fantasy is acted out but in essence it takes place in your head. That's what you don't like ... you want real danger, the knowledge you can't stop what's happening. That is the huge gap between fantasy and reality - security.