I would like to make a point, the posts of zopiclone bandit seem all to come from an angle where he believes the only reason to look at porn is to feel sexual arousal.
I believe I am not the only one that watches revolting material because the curiosity causes an urge.
Also, not everyone into BDSM is either Dom or Sub, some can switch effortlessly from one role to the other.
I've had a switch partner and part of the fun was that while being Dom we just knew whatever BS we would come up with, would surely be coming back when role would be reversed.
Also, not necessarily one wishes to directly use violence, constriction etc, towards the sub, I mostly order the sub to do that to herself.