This makes no sense to me. Look, if you support the Palestinian side in this fight, then the hief problem is that the bidy count on the Israeli side is way too low. Those missiles mean business. From Hamas' perspective they have been provoked by an enemy that sits in its borders and blockades them and refuses to alter the status quo even when violence is contained. (The insistence that Hamas modify its internal governing documents to stop expressing its interest in driving out all Zionist invaders being a non-starter, although Hamas might let it be purely symbolic if terms of a proper Hudna seemed reachable.) So of course you launch missles. It seems to be the only thing that gets Israel's attention.
And while the assassination of Jabril intensified things, it was not itself the causes beli. The Jabril assassination was in response to the massive escalation of rocket fire, in the hope by Israel that a precision strike against the Hamas military high command would demonstrate sufficient capacity and military intelligence to strike with pin-point accuracy would make air strikes unnecessary and/or cripple Hamas response to airstrikes.
One reason I get on with fat on this is I understand his view. If I were Palestinian, I would probably share it. But I'm not. So in the confused and morally messy reality I go with tribalism and while I think Israel has made a hash of it by refusing to negotiate for PA sovereignty on terms Israel can influence through negotiation -- when the shooting war starts I want Israel to win. That means minimizing Israeli casualties while trying to inflict sufficient damage on Hamas to get them to settle for cease fire. Yes, by all means try to keep the casualty count down on their side as well. But there will be casualties in war and I prefer they be primarily on the other side (and they prefer the same).
But most folks I see don't hink this way. Faced with an ambiguous moral situation they opt to break the tie by siding with the group suffering the heaviest casualties. Mind you, this doesn't seem unique to the Palestinian/Israel conflict. Why do we support separatists in East Timor but not Kurdistan or Tibet? Apparently, neither Turks nor Chinese have killed a sufficient number to warrant statehood for the other side yet. (That plus the Realpolitik of not wanting to fight China or Turkey.) Perhaps the Tibetans seem to be on to something with their recent protest via immolation.
But what happens if some of Hamas' heavy weaponry finally breaks through and kills several hundred civilians in an Israeli population center? Does the morality change? How many civilian casualties does Israel need to sustain to morally support a ground assault? 100? 1000?
Either the Hamas rocket assault is justified as an act of war because of Israeli intransigence, or its not. Either way, body count ought to be irrelevant to the morality of the situation.