This is about an artist's moral right to not have his/her work tampered with.

I agree with you in the philosophical sense, but in film, the process (today, anyway) is tilted so that the artist is frequently powerless, for various reasons. I mentioned Superman II because it shows that the "official products" that we receive have quite often tampered with the artist's work to an unacceptable degree, and to show that there are some instances where a fanedit can be the only way of restoring a creative vision.