I totally agree it's the motivation that counts, what kind of drives are really behind one's need to submit and to endure bondage, whippings and (staged) control and abuse. Sure, a D/s relation can become a screen for bad abuse, both mental and physical - the Dominant wishing to prove inflated ideas about his/her ego, the slave wishing to deify Master or Mistress and get rid of some choices he/she doesn't want to handle.
We've all heard of teen girls who fall in love with convicted killers and sadistic psychopaths and write love letters to them, or even help them escape from jail, and if it works they may endure some very rough treatment and just get totally uncritical, cutting off thir own good sense to worship the psycho Master. This happens even in modern countries like the US, Britain or Sweden, but in those cases, the motive power behind isn't really the kind of trusting submission that bdsm should be about. And I guess there's also a strong lack of playfulness in those killer/damsel relationships, at least after a while.

It's no coincidence that terrorist groups such as the German RAF ["Baader Meinhof Gang") sometimes used rape and shock abuse of new converts to a cell, or forced them to do something where they might have to break the relations to their old friends or even get caught by the police for a minor crime, to make them easier to mould and blot out their sense of dignity and value. Sure, somehow similar non-con situations happen in harsh bdsm stories of kinky castles and frightening Doms, but the difference is, one is reality and outside of any erotic or personal bonding - you don't join a terrorist group to make cozy friends - while the bdsm storyline or RP is fantasy, used to explore something and then, sort of, return from, and it's totally up to anyone who's into bdsm how much you want to spice up your need for violent domination & bondage, or just for reading about it. I don't think any sensible slave honestly would want the Dom to cut out her tongue, or to spank you till you're permanently damaged, no matter if you'd feel juicily turned on by the image.