I remember reading once that when he played Yannick Noah, he got so annoyed with Noah's family making noise and applauding his errors, that he went over to their box and stood there loudly cursing them out. I think Noah also accused him of aiming balls at him in between points. Noah refused to shake his hand after the match.
True story. It happened at the US Open 89. I saw it on TV. Noah was pissed and at the net told Mansdorf,'You don't curse at my family.' Noah's sister was in the box that day.