anger is not sinful

…Anger is not sinful. It is a part of our humanity and reflects the anger experienced by God Himself. The apostle Paul stated it clearly when he said, “In your anger do not sin” (Ephesians 4:26). The challenge is not “Don’t get angry”; the challenge is not to sin when we are angry.

Anger: Handling a Powerful Emotion in a Healthy Way by Gary D. Chapman, 2007.