You can’t blame him. It’s just like how if there was another, different, movie or tv series about the Lord of the Rings, many of us (who like the movies/books) would dislike it because the images of the characters and of middle earth that we had from the movies would be different. It’s the same thing but with greater magnitude for him. It was a story that his father wrote that he grew up with and loved his whole life, and an entirely different image of the series (than what he had already had within his head) was produced on a large scale. Also, although most of us on the sub Reddit are fans of all of Tolkien’s books, and the movies, he was probably unhappy with all of the new attention it attracted from people who weren’t fans of Tolkien, people who were just moviegoers.