I don’t think a lot of people who actually take part in BDSM would agree with the comments about abusive relationships.
I think they would, because,
People who know what their talking about or who are actively involved know it’s all about trust and consent. There’s none of that it the movie and that’s where the anger is coming from, not the mere fact that BDSM is involved.
Without going into TMI territory, I’ve moved in some interesting circles over the years and I’ve a good friend who was in a 24/7 Sub/Dom relationship for a few years, so I do actually know a good deal about this. WNB is bang on the money, it’s nothing to do with the sex and everything to do with him being a manipulative control freak stalker and then packaging that up in a bait-and-switch as “hey, it’s ok, because it’s not abuse, it’s kinky.”
A dom doesn’t just take control, a sub gives it. Contrary to popular belief, it’s the sub that holds all the real power. Compare and contrast a starting point of,
“I will submit to you and do what you ask”
with
“You will do what you’re told or else”
… now, which of those sound just a little bit rapey?