> To the average person, LLMs are too useful to reject them

The way LLMss are now, outside of the tech bubble the average person has no use for them.

> on some ultimately muddied arguments along the lines of "it's OK for humans to train on books, but it's not OK for robots"

This is a bizarre argument. Humans don't "train" on books, they read them. This could be for many reasons, like to learn something new or to feel an emotion. The LLM trains on the book to be able to imitate it without attribution. These activities are not comparable.