I think its just a simple matter of aesthetics. Some people find violence ugly, and don't like looking at it. Some people think that by looking at it you're somehow coming to a greater understanding of the world or something. Maybe that is the case for some super sheltered individuals, but I doubt it's the case on the whole.

If anyone has any ideas on what the point of violence in art is, I'm open to hearing it. Obviously horror is a genre and so is gore, and people seem to enjoy being shocked. I don't think that is what McCarthy was going for though. And he wasn't going for the vengeance-catharsis angle like Tarantino either.