Christopher Nolan's villains are atypical by comic book movie standards whose villains are either avaricious or megalomaniacal persons obsessed with the fealty others should render them. His villains are in the typical mold of the comics Batman rogue gallery who wanted to destroy Gotham for various reasons but mostly they want to see the city burn or freeze the difference is that Nolan adds a modern terrorist twist to that model. The primary bad guys in his movies have profound irreconcilable social, political and philosophical differences with the city of Gotham that can only be mitigated by the city's destruction. Examining these philosophical differences can tell us a lot about the characters as well as their probable political leanings. Let's take a look at the primary villains in the dark knight's rogue gallery in Nolan's trilogy to determine what their actions and beliefs say about their characters.
Ra's Al Ghul: The former mentor of Bruce Wayne is an extreme law and order social conservative who believe that "criminals thrive on society's understanding" that you can't lead "men unless you are prepared to do what is necessary to defeat evil" and "if someone stands in the way of true justice, you simply walk up behind them and stab them in the heart." He is advocate for old fashion justice literally no trail, jury or judge an offending criminal should be dealt with swiftly and severely on the spot. Ra's is also an Old Testament type guy he believes in destroying cities and societies that have "reached the pinnacle of decadence" similar to what God did to Sodom and Gomorrah when their "sins came up" to him. Understand that he is the kind man who would Dresden style carpet bomb sin city because of prostitution, gambling, real estate market corrupted by politicians and businessmen as well as citizens indifferent to the "suffering and despair" around them.
He poses a serious threat to Batman not merely because he is his former teacher but he strikes at the heart of Bruce's sense of justice. How can a man who parents where violently killed by a petty thief protect the rights of criminals who prey on Gotham and have corrupted every institution in that city? If he wants to save the city he must risk his life to protect all of its citizens even the criminals he put away in Arkham Asylum. If given what he wants Ra's Al Ghul would be the among the greatest mass murders in history because of the millions of criminals he would have had murdered along with innocent civilians who unfortunately lived too close to their criminality.
The Joker: He is a bank robber who steals from mob owned banks and has a strange fascination of Batman. The Joker is a capital a Anarchist who believes he's an "agent of chaos" also he is a moral nihilist who views social morality as nonexistent because of their self-serving and at times contradictory nature. He devises way to puts cops and society in impossible moral situations such as allowing them to choose between the destruction of a hospital or the death of Coleman Reese, between a ferry loaded with criminals or one with innocent civilians. Even though he did not assassinate the mayor was he plan was still a success because it struck fear in the hearts of Gotham's citizens. As the perfect anarchist his mission in life is to "introduce a little anarchy upset the established order" and show "the schemers…how pathetic there plans to control things real are".
Batman's greatest enemy is the Joker because he is a criminal who has no limits therefore he can go to amazing depths of villainy and he is the one who presents with him the gravest moral threat. The war between Batman and the Joker is more than just saving Gotham form destruction but saving his and the city's collective soul. If Harvey Dent is seen as the murderous Two-Face then what hope is there for Gotham when their own white knight has murdered six people? What the difference between Batman and a vigilante who has no morals if he kills the Joker and more importantly if he does kill then the Joker wins and he will truly have the last laugh. Think about it if as a Christian the Devil shows God that you have no morals by putting you in a situation to kill than he gets your soul and similarly for an nihilistic anarchist if can get Batman to kill him than he has shown the world that the dark knight's morality never existed. Again if Batman kills the clown prince than he proves his point 'that the only way to live in this world is without rules' and if Batman break his own rules then what good are his rules.
Warning spoilers ahead so if you don't want to know anything about the character you can skip this. From the six minute screening of The Dark Knight Rises in December and another six minute screening in April as well as all the information that has slowly come out about the character we can begin to piece together his philosophy. Bane is an über left economic terrorist that attacks the wealthy of Gotham and he is a former member of The League Shadows who probably left because he is far too militant for the group. When I used the term left to describe Bane philosophy I mean that in the loosest possible sense because what connect all those on the left of the political spectrum is their strong but wildly varying belief in an egalitarian society that has a level responsibility for its members and Bane is not an egalitarian. What connects him to the left is his Occupy Wall Street view that the wealthy specifically the business class is corrupt and that's where the comparison stops because he plans to destroy Gotham by killing them. He is a plutocidal maniac who uses terrorism to influence Gotham's citizens to rise in a French revolution style rebellion against the rich and as he said in the TV spot "Gotham this is your liberation" in an attempt to provoked them.
Alone Batman cannot take down Bane and his mercenaries he needs the help of Catwoman and the GCPD. This battle against Bane is more than the rich vs. everyone else in Gotham but about finally bringing justice to a city that has never known it. In Batman Begins there was no justice criminals like Falcone owned the city, in The Dark Knight there was Harvey Dent who was the first ray of hope for Gotham until he became Two-Face and then the Harvey Dent Act provided justice for the criminals after his death but that only lasted until the arrival of Bane whom has shown the true colors of Gotham's late white knight. Again the citizens' rise against the rich has more to do with justice then the fear they have of Bane and if Batman is going save the city there has to be order and justice for all therefore he needs to step down and Gotham needs to step up. As Batman Bruce cannot give them the universal justice they want only the citizens and officials of Gotham themselves can do that because of this he must lay down his cape and cowl for good and allow the city to shape its own destiny.