Wild Theory Proves Joker Was a Real (Though Chaotic) Hero of The Dark Knight
Sometimes outlandish fan theories get so insane, that they overflow back to making frightening amount of sense.
Such as the theory posited years ago by the Reddit user generalzee that the Joker was the real hero of The Dark Knightю
It starts off with the correct observation that before The Dark Knight Gotham was a mess of corruption and lawlessness, with organized crime running most everything, public officials being on their payroll, police having no control in whole sections of the city, and everything being barely held from imploding by a masked vigilante, who, however, failed to improve things.
According to the theory, the Joker, contrary to what he said, always had a plan.
He starts off with robbing a mafia controlling bank, throughout the movie the vast majority of his actual victims are criminals, and elements of Gotham's organized crime and corrupt police who aren't directly killed by him, get exposed in the process. Those who avoid death or arrest still get destroyed financially.
However, the Joker is not content with rooting out corrupt policemen and destroying the organized crime, he also has a beef with Gotham's ineffectual but very famous vigilante.
Batman's very existence is the symbol of non-functional law and order in Gotham. However, killing Batman is pointless for anyone who actually wants to clean up the city. If he dies, he's likely going to become a martyr and an inspiration for copycat vigilantes. Instead, the Joker seeks to crush him morally, and achieves that, forcing Batman to effectively retire and fade into an urban legend, until The Dark Knight Returns.
The person whom the Joker wishes to turn into a martyr is Harvey Dent – indeed, in death Harvey becomes a symbol of a police officer falling in the line of duty.
As for the Joker's sadistic choice with the ferries in the finale, the theory posits that his intent was the exact opposite of what he professed to Batman – he engineered the situation to prove to the people of Gotham that even the most despicable among them are far nobler that they themselves believe.
As the result, we can see that 8 years later Gotham becomes a safe and clean city (until Bane shows up), even though Bruce Wayne, psychologically broken as he was by The Dark Knight's events, no longer appears in the guise of Batman to protect it.