In view of the fact that God often expressed anger toward the evil behavior of the Israelites and Christ expressed anger toward the money changers in the temple and the hypocrisy of the pharisees, anger cannot be a universal evil. Fr. James Schall has an interesting article on the Catholic Thing discussing anger. You may be surprised at some of what he says:
Contrary to what we might think, both “anger” and “wrath,” considering them accurately, are good things. Both words, however, often refer to a natural emotion when it is excessively strong and not guided by reason. Anger indicates a strong reaction. We always knew when our fathers were angry....The topic of anger comes up in Book Four of Aristotle’s Ethics. It is one of those givens in us that needs to be self-governed. We are to be angry in the right time, right place, right degree, and under proper guidance. People vary in the ease that this emotion becomes out of control. But it is possible to be either too excessively angry or not angry enough.People have said to me in the past that anger is always bad. I knew they were wrong because St. Thomas Aquinas himself says that righteous anger, controlled by the reason and not the passions, is lawful. He quotes a homily mistakenly ascribed to St. John Chrysostom writing, "'He that is angry without cause, shall be in danger; but he that is angry with cause, shall not be in danger: for without anger, teaching will be useless, judgments unstable, crimes unchecked.' Therefore to be angry is not always an evil."
Fr. Schall goes on:
The capacity to be angry is given to us by nature itself. It is part of the whole inter-related “package” of items that constitute what-it-is-to-be-a-human-being. Without it, we would be less than we are. We would be crippled, lacking something that ought to be there. Tell me what makes you angry and I will tell you what you are. The same point can be made negatively. Tell me what does not make you angry and I will likewise tell you what you are.How many people today not only fail to be angry about diabolical evils, but actually champion them as human rights? And how many are indifferent to the evil around them endangering their very souls in the light of Christ's promise to vomit out of His mouth those who are neither hot nor cold? What makes you angry and what are you doing about it? What evils happening in your midst fail to rouse any reaction at all? Never be controlled by your anger, but let it draw you to a more intimate relationship with Jesus who hates evil and loves good.