I had a girlfriend that was into it, was always consensual and we'd practice it safely.
You have a very one dimensional view of sexuality, but when it comes to anything that isn't missionary with the lights on that's a given when sex is as taboo as it is currently in the west. BDSM is a common thing, and it works both ways (and then some). Some women enjoy it, some men do - Whatever. As long as both parties are aware and practice it safely, I don't see the problem. In the context of JAV, obviously it's going to be dressed up more than what, let's say, Kink would do. Porn is still fantasy.
We all have lines we don't cross. I don't enjoy punching. Some people find the U-15 idol stuff available here unsavory. As long as it's allowed by the rules (and more importantly, the JAV industry) bringing it up in a topic where people obviously enjoy it does nothing but derail the thread into oblivion.
/shrug
Edit: Good work there Jug.