Nothing can change what has already been done, Corn. What it can change is how you perceive what has been done and what should be done next. I think what you are saying is that a man who kills, as in murder, must be stopped regardless of why he kills. I don't disagree. Where you go all goofy, in my opinion, is when you assume that understanding why people murder, comprehending the genetic factors, if any, or the more obvious social and environmental ones, in other words, adducing cause other than personal responsibility, somehow weakens the case for the need for justice. It does not. What it weakens is the smug sense of self satisfaction people get out of punishment, the satisfaction of revenge. You want to justify your feelings of revenge. I say you feel that way for the same reasons that people kill. You and a killer have one thing in common, the certainty that the other person must die and deserves to die. I am interested only in making sure that a murder doesn't murder again. What is done is done and vengeance can never undo the original crime. It just assures that vengeance is endless. You cannot get off the wheel of karma without personal death, dying to the illusion of deserved retribution. To close that door is to open the door to another world, another vision of reality, one where you have a fine view from the cross.
We know not what we do.