Our nation should have gotten a little angrier at many times in history. For example, Rwanda. If we would have been stirred to action by our collective anger to stop the killings, we could have saved thousands of lives. So anger can a force for good. But again there is the danger.
Every evil person feels justified in their acts.
The anger is a primitive response that sets those boundaries, causing an evil person to feel right in what he is doing. That is why the emotion of guilt, which was once necessary to prod primitive man into civilization, has grown useless - those who are truly evil never feel guilty. As a child, I was taught that guns were not toys. I shot my first .22 pistol at the age of six. I was never allowed to even think of touching the weapons stored in our living room gun safe, without proper supervision.