By your logic reddit is hosting a lot of "childporn" right now. Any problem with that? Have you reported them to the authorities? Why not?
I don't know what's on hentai subs because I never subscribed to any. And there was no option like the "local" here.
Yes. I do in fact have a problem with that. I'm positive reddit has received reports but they have much more money to put towards a legal team than any instance owner here on the threadiverse could have