First of all, Batman is an even more perfect Superman than Superman himself, being a regular human being with a seemingly good but wholly secular purpose. (Not surprisingly, Nolan is currently working on a Superman film as well, and I will have more to say about the Übermensch in the future.) It helps that both Superman and Batman traditionally do not use firearms. Superman doesn't because he doesn't need to. Batman, however, doesn't because of some unspoken moral code which prevents him from killing his enemies. This of course gives progressives some idyllic comfort that order in society can be enforced without guns, justifying their love of gun control as well as their love of secular supermen who can save their utopian vision from reality. But this is only a superficial progressive bias.
The real nitty gritty of the hidden progressive bias in the Nolan Batman movies shows itself marvelously in the epic confrontations between Batman and the Joker in the second film, The Dark Knight, although the same themes are visible in the first movie as well. Conservative activists have had some fun juxtaposing Joker's face with Obama's even though Obama resembles Two-Face almost to perfection. Obama is not the Joker. The Joker represents conservatives.
The character of the Joker as masterfully portrayed by the deceased Heath Ledger intrigues us with his motivations. He is, in his own words, "a better class of criminal." His goal is not money or power or even anything material. He wants only to win an argument: deep down everyone else is just as evil as he is. He goes about trying to destroy civil order to prove himself the progenitor of the future human society, or lack thereof. He is "ahead of the curve." He calls himself "an agent of Chaos," which is apparently the series' replacement for Satan, but more on that in Part II.
The mob's got plans, the cops have plans, Gordon's got plans. You know, they're schemers. Schemers trying to control their worlds. I'm not a schemer. I try to show the schemers how pathetic their attempts to control things really are.
The Joker lays out here, better than any of the heroes could have, the movie's central message. The good guys are schemers. The good guys make plans. The good guys try to control things. The similarities to the progressive vision don't stop there. The good guys in the movie believe that human beings are inherently good, and when worst comes to worst humanity will collectively do the right thing because of their innate morality, without reference to God or any sort of imposition of morality from outside themselves. The climax of The Dark Knight, since neither the hero nor the anti-hero's goal is to kill the other, is a showdown of two different faiths in humanity. The Batman believes the people of Gotham are good not only without being coerced, but even against coercion; the Joker believes they are not.
There is no one righteous, not even one; there is no one who understands, no one who seeks God. All have turned away, they have together become worthless; there is no one who does good, not even one.
Right here lies the key, not just to the movie's progressive bias, but to the very heart of the difference between conservatism and progressivism in America today, which dates all the way back to the American and French Revolutions. Progressives believe that human beings are innately good. In fact, morality is not properly imposed from without but can only come from within. Conservatives on the other hand are more cynical. Conservatives believe that human beings left to our own devices always trend towards evil, and morality must be imposed upon society from the outside. The truth is more subtle, but in the real world the conservative vision is a much better approximation of reality. In the real world the Joker is right. In the Hollywood version, the Truth is not true. The Truth is the bad guy.
Now that's whack.