Sadly, there is a (small) market for this. A few years ago, a prospective client proposed a scene inspired by tortured refugees, including photos and videos. I guess it's never too late to find a new hard limit. I take pride in helping my subs work through their sexual kinks from trauma, or whatever, so they can own and enjoy the experience as part of them, but perhaps not the defining thing of them. But that. . .that was above my paygrade.

I suspect this person mentioned isn't building a slave up but trapping them further in their trauma. Sometimes, straight-up abuse works.