Originally Posted by socool
I know I'm a little late on this topic, and someone may have already said this, but the League of Shadows only attacked Gotham because of Talia. Talia took control of the LoS (being the heir to the throne and all) and used Bane as her muscle to take down the city her father dedicated his life, and died, trying to take down. Talia didn't care if Gotham was clean or not, she just wanted her father's life goal to be complete.
Sort of. Talia represents the dark vengeance side of Bruce that strives to fulfill his father's goal of saving Gotham (but with very different methods), while Bane represents the pure need for justice from the circumstances he's experienced. Both are doing it out of their own need for justice, though, same as Bruce. They are presented as equals, both in it together, the plan would never have been that close to succeeding without the other. In either case, there are more than enough reasons presented within even the first page of this thread that back up the idea that the LOS would have wanted to attack Gotham again.
To sum it up: The LOS is a terrorist organization that disagrees with the values of Gotham's society. "When a society reaches the pinnacle of its decadence" they come back to reset the balance. The Gotham presented in TDKR is rife with examples of this (which are discussed in detail throughout the thread). It was never about street crime, it was about the balance of society and the values they adhere to. They attack Gotham because it is the biggest city that represents Western civilization, so by attacking it and changing their perception, it would have a domino effect throughout the Western world.