The line judge was already kind of pissed at Serena because she broker her racket after the first set. So she was probably trying to be kind of a smart ass to Serena but she almost deserved it. I understand how hard it is to keep your cool, and at a professional level it can't be easy, but she should really haven't have taken it so seriously like that. I mean that was almost a death threat had it been outside of the court.