In my opinion, it is justifiable for the Israelis to respond to Islamic Jihad.
Unfortunately, what will happen is the terrorizing of innocent Palestinians. A Hamas Spokesman, Sami Abu Zuhri, said, "The resistance is a legal and natural reaction to the Israeli crimes, and the Palestinian people have the right to defend themselves." It's not a frame comfortable for most Israelis. But this is different than the insinuation that Hamas had approved.
Hamas had nothing to do with the bombing, and has been less involved in violence than the Fateh party.
I'm all for holding Hamas responsible for crimes it commits. Fortunately, plenty of Palestinians had protested Hamas after a series of bombings forced the Israelis to close the border.
It is understandable for Israel to refuse negotiating with Hamas. But punishing Hamas for the crimes of other Palestinians on affirms to the Palestinians that Israel is unable to discern between the innocent and the guilty. For now, Hamas has chosen to first clean up internal corruption - a necessary task. Nearly half of Hamas supporters want a negotiated settlment with a Jewish Israel.
Israel has refused to discuss anything with Hamas, which will make it very hard for it to demand much of anything. It's not even tried to reach an agreement. But it was this refusal which indicated to the Palestinian people that negotiating with Israel was worthless, justifying the vote for the cleaner party.
So pray for the dead. Pray that the victims don't further victimize others.