I'm Puzzled

We've been told over and over again that Marilyn Manson and his music had NOTHING to do with Columbine. Nihilistic song lyrics do NOT encourage teen suicide. Violent video games do NOT promote school shootings. Natural Born Killers is just a movie and can NOT be harmful in any serious way. Gangster Rap is just good clean fun.

In short, popular entertainment is not to be blamed for any crimes. They are just songs, videos, games, comics.

OK. So if all that is true, how can a respected scholar get away with writing in the New Republic that

When violence breaks out, Mel Gibson will have a much higher authority than professors and bishops to answer to.

(The article is not available to nonsubscribers, but it is discussed here.)

Why is Gibson uniquely responsible for the actions of his customers? And why should this movie be capable of provoking violence when we all know that movies don't do that?