Bill Cosby wasn't always the affable family man that he plays on television.Angered by taunts that he didn't do enough in the civil rights struggle, Cosby once sucker punched Tommy Smothers according to Gerald Nachmans new book.Smothers recalls Cosby told him, 'Maybe I will give you a knock upside the head one of these days. I said, 'Yeah, go ahead and give it a try.'A few weeks later Cosby made good on his threat when the two ran into each other at one of Hugh Hefners Playboy Mansion parties.'I should have never turned my back on him,' Smothers said. 'He...