The Dark Knight

The Dark Knight: Why no one died at Bruce's fundraiser. In the interrogation scene, the Joker says, "For a minute there, I thought you were Harvey Dent," referencing Batman's actions at Bruce's fundraiser. First, when the Joker arrived at Bruce's fundraiser for Harvey Dent, the Joker wasn't randomly killing people, he had a plan, and part of what made his plans horrifying was his ability to tell the police exactly who he was going to kill and then kill them. Killing random bystanders doesn't accomplish that. When the Batman (who the Joker thinks is Harvey Dent) jumps out the window to rescue Rachel, the Joker expects them to be the same person, so there's no reason to keep looking for Harvey Dent at the party. Later, when Harvey Dent is being transported by police, the Joker uses an escalating series of weapons against the convoy but doesn't use the rocket launcher on the paddywagon containing Harvey Dent. The only weapons he uses are ones that can't penetrate the paddywagon's armor, and he gradually escalates to make the threat to Harvey Dent seem real. He does this to discover if they really are the same person: If the Batman shows up, Harvey Dent isn't Batman. If the Batman doesn't arrive, Harvey Dent is Batman. The Joker never wanted to kill Batman (he says as much in the interrogation scene, "I don't, I don't want to kill you! What would I do without you? Go back to ripping off mob dealers? No, no, NO! No. You... you... complete me."), he wanted to force Batman to break his "one rule." A dead Batman cannot be corrupted, so as long as Harvey Dent might be Batman, Dent must not be killed.