Training a model with artists' work seems completely fine to me. If something is out in the world and you can see it, you can't really control how that affects a person or a model or whatever.
The actual issue is reproduction of trademarked and copyrighted material. There are already restrictions on how you can use Mickey Mouse's likeness in any derivative work. That's not an AI issue. It's an IP issue. The derivative works are no different than if I, a person, produced the same derivative work.
It would be funny to me that we had to turn our attention to training AIs in IP laws.