2. An AI has a training set of every image in the world and produces an entirely unique work.
Which do you have more of a problem with?
Copyright law serves the purpose of peoples works being protected from unauthorized parties making copies of their works, and profiting off them.
It doesn't protect from technology making the production of new works cheaper, faster, more efficient. An artist using photoshop can be many times faster than one using oil and canvas.
I think the objectionable thing about the second is that the AI knows everyone's styles, and so can use them in creating something new. Even if the AI is restricted to not be able to paint an image in a certain artist style (as the new version of stable diffusion is, for instance) and the art is unique, I think part of the problem is that the AI is still (presumably) leaning on the collective styles of everyone it has trained over.
If we can train an AI over a small dataset or maybe even a large dataset of old art, or some mix in between, and then maybe fine tune it wtih a snall sampling of modern art, then I believe it would be unobjectionable, as this is largely how humans do it.
Why is it different?
The only difference that matters, is scale. And again, if I want to argue that something done 10000000000 times is legally problematic, I have to be prepared to explain why doing it 10 times is problematic as well, only less so.
I am completely aware that scale is a "thing" in legal systems. But as I said before: For scale to be important, the unscaled act in itself has to be problematic already.
Granted, things around power concentration have deep philosophical and social roots.
Could I have a dollar? What about a billion dollars?
The burden isn't on me to explain why something being scaled up by a billion is not the same.
Humans either learn art by being natural art geniuses, or by receiving instruction and learning through an iterative process (where, again, they might create thousands of art works, but nowhere near the scale here), which is very different.