I'm a little confused by the film. I do like the insanity role that he plays. The regiment that he does on a daily basis can contribute to his psychotic-ness. He randomly blurts messages of his insanity, but that doesn't stop people from how they react to him.
He has a scene where he describes his regiment, showcasing his attention to detail. Besides the overacting on some scenes - such as stabbing the homeless, there were some good parts. How he goes on to lecture about the beauty of Whitney Houston and Phil Collins while he watches 2 hired prostitutes make love to each other.
The kicker was the detective played by Williem Dafoe. I was always wondering if he knew, because he let lose some very key clues that taunted Bateman. The second encounter with Bateman, he randomly pulls out a CD - music that Bateman would listen to. I wonder if he pulled it out just to taunt him with it, as if to say, "I know." The detective never lets off too much information. I like his character.