The first responsibility of a just government is to protect its people from foreign and domestic enemies that wish to destroy them. The state of Israel lives in constant threat from its radical Islamic neighbors that seek to destroy them off the face of the earth.
Guided by a religious dogma that aims to impose its religion on all non-islamic individuals and countries through all means including violence is a reality that Israel lives with every day. The big lie in the Arab world is they somehow care about the Palestinian cause.
The Palestinian people have been given ampel opportunity to have a homeland but instead have chosen the path of violence and hate. Allowing Hamas to govern the Gaza and attack Israel daily with rocket fire has finally invoked a response from Israel and now they act as though they are victims. The Palestinians are not victims they are suffering under the consequences of their own hate. When you sell your soul to the devil you shouldn't be surprised when you end up in hell.
Israel is totally justified in defending itself and now would be wise to ignor any calls for a cease fire and should destroy Hamas through war, defeat its enemies in order to create peace. Unfortunately, war sometimes becomes the vehicle to peace. War is ugly and innocent people die. That's the realities of war.
The morality of war however depends on its motivation and justification. If war is waged for the purpose of oppressing then it is unjust. If war is waged to protect, defend and free individuals from tirrany then it is just.
Hamas provoked the attack with Israel and now they have to live with its consequences or in this case die as a result of the situation they created. If the Palestinian people ever want to have a homeland they are only going to obtain it through peaceful means and stop the insanity of hatred and violence.