Also, the way current models work is that they need to be trained on real data. It is really questionable if someone can make this kind of stuff with, say Stable Diffusion, entirely without any offensive material as training.

If they can actually do it and make these things without using any abusive material, then I think it is fair game. Nobody was harmed, nobody should care. What a person does in their private is none of anyone business if it doesn't affect anyone else.