It's been awhile since I've seen that movie. I think the point Oliver Stone was trying to make with that movie was that we all have violent tendencies in all of us. To prove it, he made NBK and in the beginning the violence excites you even though the better part of you is disgusted. In the end though, you're supposed to realize that it's not just you, it's humanity. Humanity has very violent tendencies... but he want you to be ashamed of that; so ashamed that you will work harder to overcome it.

Problem is, I don't think most people who see this movie get Oliver Stone's point. And because of this, people just leave with more violent images, desensitization, and a riled up inner violent animal.