(Proverbs 19:11 KJV) The discretion of a man deferreth his anger; and it is his glory to pass over a transgression.
Notice that spiritual maturity does not do away with “anger” (639), it simply puts it off. The NASB has “makes slow” the KJV has “differeth”. The actual Hebrew means to make long. It reminds me of the KJV translation of patience as long suffering. Mature people still get angry but by delaying it they can either diffuse it, defuse it or focus it, whichever is more appropriate.
Sometimes anger is a mark of maturity that is based on discernment. Think of Jesus and His reaction to the moneychangers in the temple. I also think He got a bit angry with Peter when He said, “Get thee behind me, Satan”. Also note that on the cross He did not call ten thousand angels as the song suggests He could have done.
So? Don’t buy the idea that anger is automatically sin. There is much to get angry about. We need to deal with it in maturity and love. Hard, but that is what spiritual maturity demands.