Let me ask you a question, do you think the joker is one to take no for an answer? Of course not! He knows his dear Batsy hates his guts, but that won't stop him! Yes, yes, he will have his bat no matter what! The Joker's words strike fear into the Batman, the first time that's ever happened. But the question is, how would he ever get away? The answer is, he couldn't. Even if he left Gotham, the Joker would find him. There's only two options, face it head-on or continue running, and he didn't know what to do.