Artists who look at art are processing it in a relatable, human way.
Yeah, sure. But there’s nothing that says “it’s not stealing if you do it in a relatable, human way”. Stealing doesn’t have anything to do with that.
knowing that work is copyrighted and not available for someone else’s commercial project to develop an AI.
And it is available for someone else’s commercial project to develop a human artist? Basically, the “an AI” part is still irrelevant to. If the works are out there where it’s possible to view them, then it’s possible for both humans and AIs to acquire them and use them for training. I don’t think “theft” is a good argument against it.
But there are probably others. I can think of a few.