>>130186945Because the whole point is that he's lying when he claims to be some mad dog without a plan.
That's literally his M.O. for the whole film. Come to people who have had their trust in other people's plans broken, and exploit their resentment. Do the whole "I may be a bastard, but at least I give it to you straight with no bullshit" bit, even though he's actually plotting and manipulating things the entire time.
He approaches the mob. They dismiss him and trust Lau's plan instead. Lau's plan doesn't work, because just as Joker predicted, Batman would still be able to get him. So, the mob goes, "okay, maybe this Clown has a point."
Dent put his trust in justice and the plan he, Gordon, and Batman agreed to. Dent feels like, despite doing everything right and putting his neck on the line, he's the only one in the past to suffer. The dirty cops who delivered him to the mob were from Gordon's office, when Gordon believed that he had cleaned up his office and the rats must be in Dent's office. Even getting kidnapped was partly a consequence of doing some gambit to draw out Joker and protect Batman.
Joker's like, "see how they screwed you over?" And Dent doesn't even care anymore if Joker ordered his and Rachel's kidnapping, because he sees the fact that Joker was even able to do that as a fault of the mob and Gordon.
The opening scene establishes this as Joker's MO. Send a bunch of guys to rob a bank. Use their distrust of each other to turn them against themselves. Walk out with what he wanted.
