Like if I download a textbook to read for a class instead of buying it - I could be proscecuted for stealing
Ehh, no almost certainly not (But it does depend on your local laws). But that honestly just sounds like some corporate boogyman to prevent you from pirating their books. The person hosting the download, if they did not have the rights to publicize it freely, would possibly be prosecuted though.
To illustrate, there's this story of John Cena who sold a special Ford after signing a contract with Ford to explicitly forbid him from doing that. However, the person who bought the car was never prosecuted or sued, because they received the car from Cena with no strings attached. They couldn't be held responsible for Cena's break of contract, but Cena was held personally responsible by Ford.
For physical goods there is 'theft by proxy' though (receiving stolen goods that you know are most likely stolen), but that quite certainly doesn't apply to digital, copyable goods. As to even access any kind of information on the internet, you have to download and thus, copy it.
This is an issue for the AI user though. And I do agree that needs to be more conscious in people's minds. But I think time will change that. Perhaps when the photo camera came out there were some shmucks that took pictures of people's artworks and claimed it as their own because the novelty of the technology allowed that for a bit, but eventually those people are properly differentiated from people properly using it.