This movie was difficult to watch. We are accustomed to flawed "heroes." We like them. They make us feel that even though we may not be perfect, we can accomplish worthwhile goals. Sherlock Holmes, Monk, House...flawed heroes.
The protagonist is this movie isn't flawed. He's a monster who gets worse as he gets older. The theme is kind of shaky because it appears to be that if a child is raised with love, he perhaps won't grow up to be a monster.
It took almost a day to come up with whether or not I liked the movie. It wasn't a "feel good" movie. But it was engaging.