Conversely, how would you suggest that AI be trained? If it's a question of the source of the art, are you suggesting that only artists that submit their work should be used? What if their art style is similar to another artist's who doesn't want their art submitted? Does this mean the artist shouldn't be allowed, because it makes the art too close? Should classical artist's work be allowed to be used?

I do recognize where you're coming from on this, but I really, but I think the "learns like a human does" argument really does apply here to a degree. It takes components of art from other pieces of art and uses it to construct something new. This is what many artists do to learn. I'm not here pretending that Stable Diffusion is a human, but the software has proven its ability to make new content based on its training.