Re: Why did the League of Shadows want to destroy a peaceful city?
I think Nolan does a fairly good job showing that Gotham is still corrupt. Organized crime may be down, but there's still a massive gulf between the rich society types and the rest of the populace.
We get a scene at the orphanage telling us that as soon as they age out most of these kids are going into the sewers because they can't find jobs and nobody wants them. It's also implied that they make up a large part of Bane's army (what other jobs would there be in the sewers?). Bruce Wayne's first comment to Miranda Tate at her charity ball was "Proceeds go to the big fat spread. It's not about charity, it's about feeding the ego of whichever society hag laid this on." Daggett was convinced paying Bane gave him power over the man. Even the action scene in the Stock Exchange has a business man casually tossing dollar bills to the shoe shiner who has to literally pick up the scraps his "better" deigns to give him, two men passing by a janitor without even acknowledging him and a security guard talking down to Bane as an idiot for wearing his bike helmet through the door (though admittedly I may be looking too much into it, maybe the security guard is that dismissive to everyone). Finally, we can't overlook just how quickly the public took to Bane's "revolution" and threw people out of their expensive apartments.
Things look better in TDKR than they did in BB at first glance, but the decadence and rot in Gotham is still there. The powerful still take from the weak, and the city is still corrupt.
Unfortunately, instead of pointing out that the LOS is using class warfare as a weapon against Gotham and having Batman confront the problems in the city that the first act shows us we get "SURPRISE, WE'RE JUST GONNA NUKE THE CITY LOL!"