Peter Jackson changed dozens of things. If he can add things that aren't in the books, he can also change things from the books.Dude. Something happens in the books, then they put it in the movie. People criticize the thing that they see in the movie. If they don't like that scene then it means they don't like it in the book (this is assuming it's unabridged, which I was referring to). Thus they are complaining, indirectly, about the book, and thus J.R.R. Tolkien.
This means he can fix things that are stupid in the book, so there's no reason to say: "It's not bad cause it's not in the book"
If he can add things he can also remove bad things.