HMMMMMM…. Something tells me you are the salty one Mr. Mature Adult.

The point of this whole movie was that, yes, society is built over shaky foundations. People will tear at each other when things go sour. It also points out how the Joker is also wrong, not ALL of the people are like that. For us to have made it this far as a society we have to be mostly good.
it also points out that

>"You shouldn't mess up the status quo because the status quo will mess you up right back" is wrong: Batman and Dent's actions pushed the crime syndicates against the wall and "forced" them to lash out. A lot of suffering is caused by this, a lot of death too. It paid off. Third movie non-withstanding. You can beat a shitty status quo and you should try.
>People don't want to kill each other: The civilian ship refused to activate the detonator because none of them were willing to live with the consequences. Among the criminal ship, there were enough people with a conscience still for them to deny the most dangerous elements among them to activate it.
>Bad actions don't necessarily undo good ones: Harvey turning to the "dark side" ultimately did not undermine his own efforts to help the city. It took Batman's sacrifice to save it but it further proves that there are good people willing to make that sacrifice.
At the end of the movie, it is proven that those shaky elements we build our society from might be upheld, even if only for selfish reasons, are strong enough. That madmen like the joker with a point to prove end up laughing all alone at the end.