Ripping a page out of a book you own or slathering it in white out is not illegal, so I don't see why cutting a scene or overlaying a black bar or, for that matter, any other forms of editing would be illegal. The copy is yours. You own it.
Selling a modified copy for a profit? Yes, that would be a violation of copyright. That's the distinction being made.
Selling a modified copy for a profit? Yes, that would be a violation of copyright. That's the distinction being made.