It was a great movie, and the video link you posted hits the nail on the head.
This movie, while depressing, totally destroys the usual liberal notions of why there is violence in the world. It’s very thoughtful, doesn’t try to tell you how to think, and is very far removed from the usual tripe we see from Hollywood these days.
I haven't seen the movie, read any reviews, or even read any discussions on it except this thread. That said, I will bet money that your statement encompasses the following:
Leftists and Liberals have the fundamental opinion that human beings and society are perfectable, and that any deviation from that "perfection" or utopia is due NOT to shortcomings in the individual themselves, but due to the evil effects that society has had on them. In their views, those evil effects are concentrated in the three general spheres: Poverty, Ignorance, and Disease (common acronym is PID) Leftists and Liberals feel that if these three areas can be addressed by their policies and programs by a smaller group of enlightened individuals, that those evil influences on people can be reduced or eliminated, crime and corruption will disappear, and society will achieve a utopia.
In short, Leftists and Liberals believe that evil does not innately exist, but is introduced by society.
Conversely, Conservatives feel that human beings are not only NOT perfectable, but that Utopia is not achievable. We believe that no matter how nicely some people are treated, how much money someone makes, or how much benefits and privileges may accrue to people, that they can still be evil in spite of those things. In short, we believe that evil innately exists. We believe that some people just ARE evil, and want to destroy and burn simply for the sake of destroying and burning. As a result, we believe the best deterrence to crime and corruption are laws and a legal system that punishes evil-doers in a consistent, reliable, and timely way. Even if we concede that legal systems are and have been imperfect, we are inclined to use them and try to improve them on an ongoing basis.
In short, Conservatives believe that evil exists, and that personal responsibility for committing evil acts is a fundamental premise. We accept that there are people out there who, no matter how much rehabilitation is applied, simply will not change them because for some people, that is their inherent nature.
Am I right in interpreting your statement in your post in the context that the Joker as just innately...evil...and he is?