Human artists have been training on the same content for decades and no one seemed to complain. You can argue that machines should be held to a different set of legal and ethical standards, but it's certainly not obvious.

Most factories are designed based on vast amounts of prior manual labor, so it's not like "automating a manual process based on analyzing existing methods" is new, either. Why is it okay to automate the knowledge of all those other craftsmen, but not that of painters?