Powerful people are not always powerful for the right reasons: and the chinks in someone's armor are beginning to show today. If you are good friends with this person, tell them that it's time to fess up to the fact that they don't know all of the answers. You'll be doing them a favor by being brutally honest. But if they aren't exactly winning any popularity contests with you, then do nothing. Just sit back and watch them do themselves in by being so smug.