Juan Cole puts the Israeli massacre in perspective:

Since the Second Intifada broke out in 2000, Israelis have killed nearly 5000 Palestinians, nearly a thousand of them minors. Since fall of 2007, Israel has kept the 1.5 million Gazans under a blockade, interdicting food, fuel and medical supplies to one degree or another. Wreaking collective punishment on civilian populations such as hospital patients denied needed electricity is a crime of war.

The Israelis on Saturday killed 5% of all the Palestinians they have killed since the beginning of 2001! 230 people were slaughtered in a day, over 70 of them innocent civilians. In contrast, from the ceasefire Hamas announced in June, 2008 until Saturday, no Israelis had been killed by Hamas. The infliction of this sort of death toll is known in the law of war as a disproportionate response, and it is a war crime.