Anger focuses on the emotions...this hinders clear thinking and cannot send the message across to the other person because of (any of the manifestations of anger, such as) shouting, animated actuation with angry facial expression, blaming the other person, clenching the fist or acting to hurt somebody..these actions either frighten the other person or make the other person angry too, so there is no communication happening...just individual display of disgust, disappointment or frustration.
