He hasn't even had a chance to take in the fact that it's Bruce there. That's something that he can deal with later, once people are safe and this whole zombie thing has been dealt with.

After all, Dick is still a Bat. They're good at repression.

"Like that's not exactly what I'm already doing."

But. That doesn't exactly stop him from snarking back, either. He wouldn't be himself if he didn't.