It just seemed, to me, that Gregory was not listening to the answer at all, but was already thinking and reading ahead to the next question.
In 1995, Newt was on Rush's show, and they were talking about conversing, when Newt came out with the gem "The absence of speaking is not listening".
He expounded on this, by saying " Most people in the news are more worried about the next question they are going to ask, that they don't listen to the answer to the question that they just asked.
He really didn't challenge Chertoff much. We've seen him much worse, but today he just filled Timmy's chair and played it relatively straight.