The manager oversees and has final say on all on-field decisions. Once again I will ask, when people are angry over personnel decisions, where do you think that anger should be directed? We won the game, so no one can blame Gibbons for anything. He's taking heat because of questionable use of his pitchers, a decision that is ultimately up to the manager.
People are upset about Estrada being left in the game, and directing their anger towards the guy who made the decision. Not really sure what else you would like them to do, maybe don't read the John Gibbons venting thread of you don't want to see people venting about John Gibbons.