There he was standing over a bronco player with no souths player touching him.
His options? Do nothing until the bronco moves, if he starts to run - tackle him. If he stands up and plays the ball appeal for a voluntary tackle, or simply put a hand on him to complete the tackle.
None of those suited his mood he dropped hard on the player and a melee erupted. He gave away a penalty and should have spent ten in the bin considering he was penalised and warned a couple of minutes before.
The bin, in my view, should be used to cool down out of control players. Refs are too reluctant to use it.