The concept of a species of intelligent creature that is naturally inclined to servitude and loves it is actually a very interesting concept. There’s nothing wrong with exploring such a concept in a fictional setting.
Not that they were really explored in the Harry Potter books, but I could certainly see such an exploration being fascinating, since it is wrong to enslave a people and it is wrong to prevent them from doing what makes them happy and fulfilled…which happens to be serving.
Incest porn that was actually labeled as such was pretty common about 15 years ago. By which I mean pretend incest, the performers were not really related but were pretending to be.
But there was some case where a woman was posting porn of herself and her son that got really well known. After that, I’m not sure whether because of some new legislation or because of just covering asses, they started calling it step-incest instead of pretending it was real.
In my totally anecdotal experience, incest was getting pretty popular before that time, then it dropped off for a while, and is now picking up steam again. I’m even starting to see slightly more stuff that pretends to be real incest again instead of the stupid step-incest.
It would be nice if it was easier to filter out what you don’t like though.