Yes you are correct in the rhetorical question and if he had left it at that , no body should say anything . After asking the rhetorical question he then said see nobody can answer that question . When he used the follow up statement he in effect was no longer asking a rhetorical question and IMO challenging the audience and thats what got the response .
As of this date 8-18-14 at 6:42am I became a proud grandfather I guess I'm officially old
HAPPY BIRTHDAY TO HIM