Violence always shapes political discussion. When someone commits a terrorist act, there must always be a decision made on how to respond to it.
Understanding what drives a terrorist does not necessarily negate any punishment for the act of terror. It does give you the opportunity to decide whether the grievance that led them to act is one that you agree is legitimate, or if not, perhaps it is one that you want to address anyway in the interest of lowering the risk of other terrorist acts. All of this can be done without excusing in any way the act itself.
Understanding what drives a terrorist does not necessarily negate any punishment for the act of terror. It does give you the opportunity to decide whether the grievance that led them to act is one that you agree is legitimate, or if not, perhaps it is one that you want to address anyway in the interest of lowering the risk of other terrorist acts. All of this can be done without excusing in any way the act itself.