I for one find it hard to believe that any one in their right mind would kill their own child because they killed someone else. After all, that is their own flesh and blood. Parents tend to care for their children, over every thing else in this world. Furthermore, if the man referred to in this paragraph followed his words, would it not be right for his father to kill his son because his son killed his grandson. The cycle of violence never ends when you follow the eye for the eye.
Many people say an eye for an eye.
I submit to you that when you follow that, for each person that is killed whether it be murder or revenge of a murder, still another murder could occur, simply because the second party sought vengeance. This happens daily in our society. Just look around at what is going on today. Look at the gang problem. Out of revenge the second gang will strike back with another fatal blow.