On a brisk Thursday evening in mid-November, I sat high in the stands at a Denver Broncos home game, covering the ears of my 4-year-old son as the fans around us launched f-bombs at Tim Tebow, the Broncos' struggling second-year quarterback. Mr. Tebow was ineffective and off-target for most of the game, and one of his more voluble and obnoxious critics was standing right in front of us.

But the heckler's friend wasn't joining in. "Just wait until the end of the fourth quarter,"...