Hamas is a terrorist organization, Dr. Guy, and they installed terrorists in their government positions. Our own government espouses the killing of terrorists to prevent further attacks. Sometimes it isn't about whether or not terrorism will end, it is about a job that needs to be done. Hamas officials will not allow themselves to be brought to justice, so, there's not much else you can do.
Eventually, hopefully, the Palestinian people will have a glimmer of wisdom and elect leaders that look to their best interest, instead of organized crime figures who profit from their suffering. Until then, they commit acts that require answer. Peace is not served by ignoring murderers there, any more than it is here when we send them back out onto the streets to kill again.
The difference is, there they have the resources of a small nation to fuel their evil. We've heard the argument before that killing, say bin Laden would just spawn more like him to appear. Should that stop us? We beheaded the leadership of an entire nation after 9/11. It would by hypocritical for us to condemn what Israel is doing after they have lost so many.