Seems to me libel would require AI to have credibility, which it does not.

It's a tool. Like most useful tools it can do harmful things. We know almost nothing about the provenance of this output. It could have been poisoned either accidentally or deliberately.

But above all, the problem is ignorant people believing the output of AI is truth. It's pretty good at some things, but the more esoteric the knowledge, the less reliable it is. It's best to treat AI as a storyteller. Yeah there are a lot of facts in there but when they don't serve the story they can be embellished. I don't see the harm in just acknowledging that and moving on.