Moore has been burned badly by the earliest adaptations of his stuff. Read the first two volumes of League of Extraordinary Gentlemen. Then watch the movie. Read "From Hell", which is maybe his best work. Then watch the movie. I would be a little bitter.
Still, it's short-sighted. Raymond Chandler was once asked how he felt about Hollywood destroying his books. He just pointed to his bookshelf and said No, they're still there. Even a bad movie gets more people to read the original book, and that's a good thing for an author.