In 2011, the San Francisco 49ers hosted the Oakland Raiders in a preseason matchup that would become a seminal moment for fan violence. During the game, seventy fans were ejected from the stadium, one person was beaten unconscious in the men s room, and two men were shot in the parking lot after the game. This is hardly an isolated incident. At any given game, fans get kicked out and arrested for acting out. In the spring of 2014 alone, soccer headlines screamed of a fan killed in Brazil, a supporter who punched a police horse in England, and three fans shot in Italy. But why do fans resort...