They might be going for "The Killing Joke" origin story where he was a struggling comedian, or at least something similar, and eventually have him become the monster we know and love. If that's what this is, I might be down.
Okay in all seriousness I don't know what you guys are upset about? Trailer looked great to me.
... because its a contextless art picture claiming to be about a character that really only has any value in his jux ta position against another character who isn't even in the movie? Because it takes a character whose main character trait is that he's a remorseless force of the cosmos imposing chaos for no reason other than whim and tries to make him a sympathetic character? Because the ostensible protagonist is the $#@!ing Joker, a guy primarily known for murdering a teenage boy, psychologically and physically torturing his paramour, attempting to drive a police officer insane, shooting a young woman with the specific intent to paralyze her... I mean, I could go on, but yeah, this is not a guy I'm rooting for.