I think this is indeed some dangerous development for AI, if such lawsuits are successful.
I don't really see why humans are treated different than a computer, for this case. A human also learns from lots of copyrighted material. It's not possible that whatever a human has seen or has heard, will have no influence whatsoever on the human brain. So by the argument here, everything what a human does, ever, is always derived work from everything he/she has ever seen in his life.
So, then another argument is, of course there needs to be some line. It's only derived work or breaks copyright if it is really similar enough. But if this is now the argument, where is the problem? We can just apply the same to the AI. Of course, this is somewhat ambiguous, where to draw the line, but it's just the same as for humans.
Another argument is, the AI has in total seen much more visual data or text, than any human ever could in his/her life, so that is how the AI is in any case different. But I don't really see, why is this relevant? Some humans are reading more books than others. So those who have read more books are in danger, at some point to have read too much books? Where is that line?
Another argument is, stochastic gradient descent works different than the human brain learning algorithm. I don't really see how the details of these technical difference are relevant here.
Another argument is, the human learning is much more efficient in terms of data. But I don't understand how this is relevant here. Isn't this actually an argument in favor of the AI regarding this topic?
Future research on AI might make the AI, its behavior and its learning, more similar to humans. But if we now have a law which says it cannot use public copyrighted data to learn, then the AI has a huge disadvantage to humans, because humans use such data all the time to learn.