I'm thinking here, not sure where I'm going.
Thinking about sexual violence (for me) starts with Story of O. It was extremely violent for its time and the first bdsm story I read; I'm sure that's true for many here. Most commentary I've seen and heard of assumes that O was a victim, but she has always been a heroine to me because, like everyone who tries to understand pain and other dark subjects, she was a volunteer. She was an independent professional woman when they were vanishingly rare; her possible suicide never made sense to me. I think it was a sop thrown in to mollify shrinking violets and moralists. Don't let me get started!
I think fictional violence and our reaction to it serves many purposes. Sometimes it's just a phantasy (Texas Chainsaw, Freddy Krueger, ... come to mind although I've never seen them), a Halloween spook. Sometimes there's something else going on (Dirty Harry), sometimes it's a cartoon (Terminator). Sometimes writers and readers use fictional violence to work on something that happened to them or that they're worried about.
We're a violent species that's tried for just over 200 years to convince ourselves that we love peace. That's 200 against millions of years. We are all capable of murder if the right (wrong?) circumstances occur.
Bottom line: Whether people who post here are as sane as anyone else or as whacko as Freddy Krueger, I'd rather have them writing and posting stories than acting out their dreams.