I think you don't know how laws and Author rights work

The simple fact his work became part of something else he did not authorize is the problem here.

And yes, it could spit out something that is very close to the original, so close that fair use could not stand.

Fair use is not a right!

> If your friend is still upset, maybe they should consider the artists they "stole" their learning material from.

He does, don't imply differently, ad hominem are a stupid argument for very stupid people.

That's why he spent 30 years of his life learning and in the end he became good enough to meet the artists he "stole" from to thank them of what they did.

You seem to lack the ability to understand the difference between being a good person and being a senseless automata...