There is no cause for anger
In his book The Sermon on the Mount: The Church’s First Statement of the Gospel, David P. Scaer draws out the true teaching of Jesus, obscured by textual assertions that accommodated man’s tendency to justify himself: there is no place for anger in the life of a disciple of Jesus.
Jeffrey Gibbs’ excellent article “The Myth of Righteous Anger” expands on this and is highly recommended.