I've seen similar things happen in low level hockey matches. I remember watching an indoor match where one umpire kept giving everything to one team. I shouted out about one particular decision - effectively telling the umpire to stop giving his own club decisions.
What followed was quite funny. He marches over and tries to red card me as a spectator. I laughed in his face. He starts to ask for my name - I tell him I'm not linked to either club, that I'm no longer an active player and that he is just following in the grand tradition of biased umpires from ABC Hockey Club. He looks bemused - says I've no right to be there - I point out that this is a Council facility and that I have every right to be there. I also then proceed to quote the laws of the game that he has blatantly got wrong. By this point the steam is coming out if his ears - and he has to be dragged away by his team.
A few more spectators joined in with me - alternatively booing and cheering when the umpire got a decision right or wrong. As the game progressed you could clearly see that he was consciously avoiding us booing him to the extent that he actually gave decisions against his own team that really should have gone the other way.
His team got the message though - for the next match they had someone else umpiring.