The line is right at the very end, but if you watch the whole clip, you see how the interview goes from questions about the movie to questions about Downey's past. I like it as the parting shot.
I post this only as an interesting example of how you end conversations when you're done. I thought Downey did it quite well. It wasn't a mean comment, but it made clear that he really wasn't interested in talking about the touchy-feely stuff about his past.
I also like the little jab Downey gives him (around the 5:56 mark), saying that the interviewer's "foot is starting to jump a little bit" so he better go ahead and ask the next question.