slave-fic writer here: I think it might have something to do with the fact that the slavery stuff was the first kink that was ever mentioned in the meta? Like, I think there was one post that mainly said 'why is there so much slavery stuff, I'd like to read sth else???' and then a second post agreed, and that was it, then, which, eh. Harmless. I mainly thought 'noooo, for once the meme is chock-full of my fav trope, this is perfect, don't say anything to make it stop/How dare you imply that pretty characters in collars aren't the pinnacle of literary achievement etc' but I couldn't even be bothered to make a comment. Judging by the amount of slavery AU fic existing across many fandoms in general, I also wouldn't ever call writers and readers of it a strange minority. I mean, the tropes I work into my fics don't come outta nowhere :p