I don't think Batman ever needed a better reason than the one he got during the Golden Age when he caught Joe Chill and Len Moxon, being Batman is perhaps the best use of his unique set of skills. Anything more than that is just window dressing. But then, I'm a sucker for heroes who are heroes because it's the right and proper thing to be.

I think Dick maybe talks to get them to talk, which means that they're splitting their attention between their plan, and talking to him. I don't think it's white noise, as he will be asking them pertinent questions and making use of the answers.

Again, my touchstone for such things is Terry McGinnis' final showdown against the Joker in BB:RotJ, a masterclass in how to use a villains vanity against them.

http://www.youtube.com/watch?v=tOP_EprkZCk (about 4 minutes in, though the first four minutes are great too)