He wasn't convcted for crimes from 35 years ago, he was convicted for a crime he committed 10 years ago. His crime, might I remind you, was DRUGGING and FORCIBLY RAPING a woman while she was unconscious. Bill Cosby is a true criminal. Stop making false equivalencies and trivializing sexual assaults.
Actually they chuckled because he did the most stereotypically American thing possible: boasted about how he's grown the economy. To the majority rest of the world, such statements are brash by nature. Their laughter was in no way connected to the veracity of his claims.