If OpenAI's output reproduces a copyrighted image with one pixel changed, is that valid in your view? Where does the line end?
Copyrighted material should never be used for nonacademic language models. "Garbage in, garbage out." All results are tainted.
"But being forced to use non-copyrighted works will only slow things down!"
Maybe that's a good thing, too. Copyright is something every industry has to accept and deal with -- LLMs don't get a "cool tech, do whatever" get-out-of-jail free card.