I think that's the difference right there.
One is up for debate, the other one is already heavily regulated currently. Libraries are generally required to have consent if they are making straight copies of copyrighted works. Whether we like it or not.
What AI does is not really a straight up copy, which is why it's fuzzy, and much harder to regulate without stepping in our own toes, specially as tech advances and the difference between a human reading something and a machine doing it becomes harder and harder to detect.
Is "intent" what makes all the difference? I think doing something bad unintentionally does not make it good, right?
Otherwise, all I need to do something bad is have no bad intentions. I'm sure you can find good intentions for almost any action, but generally, the end does not justify the means.
I'm not saying that those who act unintentionally should be given the same kind of punishment as those who do it with premeditation.. what I'm saying is that if something is bad we should try to prevent it in the same level, as opposed to simply allowing it or sometimes even encourage it. And this can be done in the same way regardless of what tools are used. I think we just need to define more clearly what separates "bad" from "good" specifically based on the action taken (as opposed to the tools the actor used).