The Galaxy lost 4-3, with the game ending in controversy as David Beckham sparked an all in brawl.
"The referee had no clue to what's going on," Arena told reporters. "There were a couple of handballs in the penalty area he missed, he did a poor job of managing the game.
"The reason there was that disturbance at the end of the game was that I think he didn't take control. You had two competitive teams and things boiled over. I thought the management of the game by the referee was atrocious."