Many of us are still children!The mother shouted at the child, "Why are you beating him"? The child replied, "He beat me first and so I have to beat him in return". The angry mother intervened to stop the fighting children. She tried to make him understand that beating hurts, but the child remained firm in his logic about why the other one has beaten him first.
Or take the case when the father rebuked the child for scoring poor marks. The child quickly retorted that his friend has scored even lower. These are all childish affairs and many of us have experienced this during our childhood. In all these cases, the children have to be handled properly so that they can understand what is right and acceptable and what is not. There are many children who are revengeful. Well, why blame the child there are more adults who employ revengeful tactics in different situations in life.
Justifying wrongdoing by giving an example of another wrongdoing by the other person is another tactic of revenge. Actually, we see this justification from the people around us and the politicians all the time. Whether it's their disruptive activities or abuse of power, they will try to justify them by comparing it with the wrongdoings of the oppositions. It seems many of us are still children while trying to justify our wrongdoings.