Originally Posted by The Joker
Yes absolutely I believe him about Batman. No question about it. He turned all of Gotham into a murderous mob after Reese just to protect Batman's identity because a world without Batman to him would be boring.
He wanted to kill Batman before, but as soon as he sees that Dent and Batman aren't one in the same (when he sees the Batmobile flying down the tunnel), he makes it a point for the rest of the film to not kill him. The interrogation scene reveals this.
He saw he wasn't ordinary, that he was a "freak" just like him.
Before he wanted Batman's blood, sure, but not after the "hmmph?" in the tunnel.