I enjoy reading non-consensual type stories a lot more than those stories of "well, he was raping her, but then she decided she really liked it five minutes in." It's not that those stories can't be good too, but...man, it's a fantasy. My fantasy doesn't have to be PC. BDSM is, for most people, about dominance and submission, and rape is the ultimate way to act that out. Of course it's a terrible thing in real life, and of course I wouldn't want to be raped. But I also probably wouldn't really enjoy killing orcs with a sword, and I sure do like me some Lord of the Rings.
Now, some stories do go a bit far, I think, in terms of the absolute degradation of women. And let's not even get into some of the racist crap. But these are rare, and the common thread is that they are badly written. As long as the writing is good, it is still a bit of art like any story, playing off of human emotions. I've had forced sex fantasies since I was 12 years old; if that doesn't make me a sick human being than it doesn't make you one either.