Barnes is asking big things from Ament and benching him when he can't deliver (first half against A&M). He's asking little things from other players and benching them when they can't deliver.
Sure it's frustrating when Barnes benches you for letting your defender blow by you, but that's literally your job and you failed. Ament is defending his player, the passing lane, and help defense in the paint, rebounding, and initiating or finishing transition offense. Not without mistake but as well as or better than his teammates.