Anger as I speak of it, is unrighteous in nature. This is not the anger exemplified by Jesus in driving out the unrighteous from the temple. Nor is it the type of anger admonished by the psalmist and Paul: requisite is that it be free of sin [Psalm 4:4, 37:8; Ephesians 4:26]. The anger I speak of is tyrannical in nature. It is the anger of a crazed king Saul [1 Samuel 20:30-31], or of the New Testament zealous persecutor by the same name [Acts 8:3].
As a man who struggles with bouts of anger, I am convinced that the root of most anger is pride of the worst kind. It is pride that is deserving of death in the Kingdom of God [Prov 16:5]. Pride perverts the mind and perspective in such a way that a person actually thinks the world—people, objects, events—ought to be ordered in such a way as to serve that person at every turn [Prov 19:3].