User-generated (legal) adult content is no different than a blogpost about a cat. If it can get rewarded through a Tribe like Dporn it's just a good incentive to put it there compared to any other website.

If a user likes to make adult content anyway and putting it online, they might as well use dporn and get some tokens instead of nothing somewhere else.

Getting things deleted will be tough. But that's already the case on the internet today.

People that watch the content can be anonymous. If they want to reward the content they can be anonymous too.