It started early in Trivium's set. The lead singer paused between songs because apparently someone spit on him. He didn't see who it was, so he spent a couple of minutes trying to call the person out, but no one would admit it. Later, some people were yelling 'Fuck Trivium' and the lead again stopped between songs. This time he he asked "Why don't you like us?" They yelled back something I couldn't hear. He said "Is it because we're not European? Are you anti-American?" It went on a little longer, until the singer basically said "I've got the mic, so have to listen to everything I say." Finally they started playing again.
It was pretty pathetic, and showed how insecure the lead of Triviumis. If he had more class he wouldn't care if people don't like him. It got worse, because he kept demanding that people start a circle pit, over and over, "Start a fucking circle pit, San Francisco!" A better band wouldn't have had to ask.