The angry person reacts in anger and causes others to be angry, and a cycle begins. My hope is that I'm able to be a person who ends such a cycle, a person who reacts to anger with love and understanding, because the angry people need that more than anything else. We can't psychoanalyze everyone we meet. We can't say this person is angry because she's been neglected, or this one is angry because he's trying to compensate for feelings of inadequacy. We need to separate the anger from the person, the creation of God who stands before us and who deserves our love.
Love is the only power that can cause a permanent change.
There is injustice in the world, and as Arthur Ponsoby points out below, if our lack of anger is a sign of indifference, then it's a big problem for us and for those people with whom we share the world. But we still have to control this anger, as Aristotle points out below. Unchecked and misdirected anger is destructive, and if we're to be angry at all, we want that anger to be constructive, not destructive. Controlling our anger takes learning and practice, and we have to keep learning from our mistakes and the mistakes of others to learn how to use our anger effectively, and to know when to recognize anger that's justified, and anger that's a reflection, a symptom, of something else that's going wrong in our lives. Anger destroys the angry person and all those around him.