Some people are not wired right and some have troubles getting any erection from normal stuff, turning to more and more extreme. I am glad people who like gore have drawings for release so that it is victimless, but any exploration into real people should be punished even when consensual, because in my book, two crazies don't make it okay when someone is getting mangled and scared in the process, even if one is dead already.
Giving them social acceptance is also dangerous, because it just isn't okay and is quite dangerous for it to be okay.
This doesn't apply to a bit of blood letting, being tied up with a bit of pain, or other not so harmful things. And I think that drawings need to be available, but nothing else. Because when it comes down to it, drawings do not hurt anyone.