Paul, writing to the Ephesians says - “When you get angry do not sin … ” (Ephesians 4:26) which suggests that not all anger is sin and there’s a way to get angry and not sin. There are some things that are just wrong and we should be angry about them. Anger can be an evidence of love and we can get appropriately angry because we reflect God’s image.
But there’s an anger which is not appropriate: an anger which is selfish, self-centred and uncontrolled, an anger which arises in our hurts, frustration and fears. Matthew, in his gospel encourages us to - “Grow up. You’re kingdom subjects. Now live like it. Live out your God-created identity.Live generously and graciously toward others, the way God lives toward you.” (Matthew 5:48)