The potential output. You train on movies and animation and you get a model that can

- produce your own movies/animation - identity movies/animation from context - identify actors/characters and cross-reference them in other works

You apply these parallels with porn, a more anonymous and intimate setting, and you can see how the kinds of results can be more morally dubious. And that's before getting into if the kinds of porn being trained on is even legal in your given jurisdiction.