This is probably mine too. 0 to fisting while fighting back was so intense, just knowing I couldn't stop it. I don't even really like the fisting (when the guy pops his hand back out it is unsettlingly close feeling to childbirth) but he knew it was the far edge of what I am willing to do. We didn't work it all out ahead of time as we had a lot of experience with each other.
It is both hot and sexy and also upsetting and cathartic and just overall a peak experience.
Yeah I am glad there are guys into it, and in an ethical way - I can't do the other side, someone who says no just shuts me down, turns me right off. But for me saying 'please no' is even hotter than 'please' somehow. I gave up on trying to understand or fix it once I figured out that submissive was not equal to passive at all, wasn't some form of laziness.