Anger: An emotion felt when we believe we have been wronged.
Aggression: is an act of expression of the anger, by our words our actions. Aggression can be insults, sarcasm, shouting or physical forms like breaking things. It can also manifest itself in stress, loneliness, anxiety, guilt, or awkwardness.
When we criticize the anger, we are providing fuel to the fire, leading to further aggression on the angry person's part. If we ignore and give in, we are setting a wrong example and the person learns that it is ok and effective to be angry.