Anger is not inherently good or bad, but is right or wrong depending on its motive and its object. Righteous anger, in fact, is necessary for a healthy humanity – to be confronted by gross injustice and not be angry would be inappropriate and (perhaps even) evil. But nevertheless, it’s clear that anger can sometimes be incredibly damaging.
What is the difference between righteous anger and damaging anger? Righteous anger happens when the character of God has been challenged; unrighteous anger happens when our own glory and importance has been challenged. But whether it’s righteous or unrighteous anger, it should be temporary since anger is a sign that something is wrong. In other words, harboring anger – for any reason – is sinful and damaging. Ultimately, righteous anger is validated by God’s righteous anger against sinfulness, but God’s anger is temporary since he decisively acted – in the death and resurrection of Jesus – to rid the world of the injustice and evil that has caused his anger.