It is possible to discuss this subject. Juan Cole enlightens us a little on the inevitable claim "but Hamas has been lobbing rockets at Israelis for years from Gaza!"
Juan Cole tells us about these rockets, and provides some perspective:
There is more to read at FDL and of special note is the situation with respect to food being allowed into Gaza by the Israelis. Basically, the Palestinians are being starved to death in addition to being bombed.
Israel blames Hamas for primitive homemade rocket attacks on the nearby Israeli city of Sederot. In 2001-2008, these rockets killed about 15 Israelis and injured 433, and they have damaged property. In the same period, Gazan mortar attacks on Israel have killed 8 Israelis.
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.