Once a customer has bought a legal copy of the movie, I believe he has the right to modify it in any way he chooses, or to pay someone else to modify it for him.
Would you defend someones right to do that? You can't have it both ways. Copyright owners either have the right to control what they copyright or they do not.
I don't want it both ways. I want the legal owner of a legal copy of the material to have the right to modify it if they so choose. I want to have the right to tear pages out of the book I just bought, or to draw a line through a sentence and replace it with my own. ...or to black out all the bad words.
Or, I want to be able to pay someone else to black them out for me before I read it. I have paid for the book, I should be able to do whatever I want with it after that, shouldn't I?
Now, if editing my own copy of a book is legal, and if paying someone else to edit my copy of a book is legal, then why isn't it legal to have the book store that sells the books edit my copy of the book when I purchase it?
The book would not be edited for all readers, just those who want the edited version. The editing service would be obviously performed by the book store, not confusing anyone that the author's original work had no offensive language.
All we're talking about, when you get to the essence of it, is the performance of two legal services: the sale or rental of legal copies of movies, and the editing of those legal copies for content in such a way that it is clear that the content is not the original work, and both services being performed at the same time, by the same business.