Look – we all get mad. The question is what are you going to do about it? Anger directed towards people is rarely productive. In fact, seeking revenge out of anger is decidedly counterproductive.
On the other hand, righteous anger about injustice can be channeled into really productive actions to alleviate the injustice. And there lies a critical difference. Anger towards people often results in bad emotions and bad outcomes. Anger towards a bad situation can spur people to action. And if channeled properly, towards good actions that alleviate the problem.
What you want to avoid is getting angry at the people causing the injustice. Because getting angry at people rarely helps you solve your problems.
So, to recap: if you are angry, focus on solving the problem and try not to get too angry at the people causing the problem.