Most people who are aware of the situation on the ground, including many experts on the issue, say that it was the Israelis who broke the cease fire not Hamas. The rocket fire for example after the cease fire according to Israeli sources, went from something like 130 to 3. So Hamas was abiding by the cease fire. Israel however, did not lift the blockade as was agreed upon, which lead to huge shortage of the basic supplies, which in itself can be seen as an act of war, and they also killed 13 Hamas men in a clear violation of the agreement. So by your own logic, Hamas was justified in defending themselves and firing the rockets that apparently caused this. But sadly, Israeli/American propaganda is such that you never hear the other side. Anyways, there are other reasons why Israel does not deserve any support. The biggest being their continued occupation of Palestinian and Arab territory, and their expanding settlements on occupied territory. It a clear violation of international law.
I have no doubt in my mind that Israels action is unjustified.
The only reason for Israel to have done this is to terrorize the Hamas to discourage them from terrorizing Israel.
Hamas and Israel dont like each other and are sworn enemies. Hamas has said that it will not legitimize Israel and Israel goes and eliminates Hamas leaders.
What Hamas is doing is playing into hands of Israel. If Hamas wants war, they will get it from Israel. The problem is Hamas cannot match Israels force. Hamas dont recognize Israel and declares to eliminate Israel. This is what Israel wants. Israel wants an excuse to advance its settlement and put the future of Palestinians in the hands of Egypt and other Arab states.
By recognizing Israel and agreeing for a ceasefire, Israel will loose any excuse to attack Palestinian lands. This will also build confidence in Israel that Palestinians and other muslim countries are not bent on eliminating them.