Well in a way I think that was the point of TDK, its comes out in the conversation Alfred and Bruce have towards the beginning of the movie, and throughout. How Bruce is overstepping his bounds, not realizing HE has limits, not separating from the Batman persona, Batman was meant to be a symbol not a symbiote, he can't see that and is blinded by his "duty"...that's the point of The Dark Knight, the difference between man and monster, between was is perceived right and what's actually doing good for Gotham.
Between living by self imposed rules or being willing to do anything to actually stop evil. Had TDK Batman in the beginning of the film met a Joe Chill type in an alley, another child's parents would've been shot because he wouldn't have it in him to stop the criminal instead of looking to stop "crime". But by the end, when he saves little Jimmy Gordon, and kills Harvey. He learns what he has to become.