Alan Dershowitz writes in the Wall Street Journal that "Israel's Policy Is Perfectly 'Proportionate'" :
The claim that Israel has violated the principle of proportionality -- by killing more Hamas terrorists than the number of Israeli civilians killed by rockets -- is absurd. First, there is no legal equivalence between the deliberate killing of innocent civilians and the deliberate killings of Hamas combatants. Under the laws of war, any number of combatants can be killed to prevent the killing of even one innocent civilian.
Has Dershowitz not read that at least 25% of the Gazans killed by Israel in the past week have been civilians? Did he not read that in killing Nizar Rayyan, a senior Hamas leader, Israel also a killed his two of his four wives and eleven of his children: ages 2, 3, 3, 4, 5, 5, 6, 12, 12, 15 and 16.
By Dershowitz's stupid legalistic logic it would be OK for Hamas to kill any number of Israeli soldiers to prevent a future recurrence of such Palestinian civilian deaths. So, if 4 months from now, lets imagine, Hamas where to somehow kill 10,000 Israeli soldiers - let's say by poisoning the water at an IDF facility, that would be just fine with Dershowitz. (10,000 represents the same ratio of killed civilians to soldiers: 3 Israeli civilians killed, to 300 (estimated) Hamas operatives(*) killed so far in this war.)
Now I am not saying that wars must be exactly proportional, but some proportionality must exist. Legality is not the issue. Morality is. And of course Dershovitz completely ignores the fact that Israel kills civilians too.
(*) And we won't even go into the fact that not all 300 Hamas operatives where terrorists. This number included police cadets, prison guards, and government office workers.