Japanese horror movies and Japanese culture?

First of all I like Japanese culture very much, so don`t get me wrong. I just cannot help but being surprised by the fact that the most gory movies in the world are Japanese (Guinea pig series, visitor Q, the ring..). The reason behind my surprise is that Japanese people look really nice, peaceful and polite. They seem to value family and social stability. How do they produce and apparently enjoy watching such horror movies, which breaks all social norms ever known?