The Dark Knight of four years ago had a villain, the Joker (Heath Ledger), whose evilness had no affiliations and whose incendiary insanity burnt everything in its way. That included Batman (Bale), Police Commissioner Gordon (Oldman) and a District Attorney, Harvey Dent, who was almost the 'White Knight' everyone wanted till the burden proved too much. It hinted at the pointlessness of terror and the dilemmas faced by those trying to fight it. Batman constantly struggled with the boundaries of goodness in the film, and ended up taking all the blame so that Gotham could be left with a blemishless hero they wished to believe in, Dent.
Four years later -- eight years in the film -- The Dark Knight Rises has moved on to other pressing social issues. The Dent Act that resulted from the previous Batman venture has led to criminals deemed "hardened" being put behind bars endlessly "without parole" -- read anything there? Meanwhile, the moral dilemma that frequently washes up against Wayne's tortured conscience has to do with the inequities of a society where a privileged few live it up at the cost of many -- ring a bell?
The nuclear bomb dressed in an inexplicably ornate shell -- which could alternatively serve as "the earth's only answer to sustainable energy" -- is just a ruse to throw a Russian rogue scientist in as well as an end-of-Gotham scenario (curiously, nobody is talking the world here).