I believe that Israel has done everything humanly possible to avoid civilian casualties, short of weakening their military efforts to a point where they would be ineffective. This is generally the way of war in western civilization, where some rules actually apply, unlike Islamic culture, where slaughter and suicide bombings are the norm in Jihad.
This has everything to do with WWII, and the concept of a "Good War", or "Just War". In that conflict, civilization was facing the threat of world fascist domination, and used carpet bombings, fire bombings, and nukes to kill hundreds of thousands of civilians (purposeful, in many instances) in order to survive and DEFEAT THE ENEMY. If the UN had been running WWII, we would be living in a fascist world today.
Israel is also justified to do the same, and has shown great restraint, probably too much restraint, in my opinion. What is happening in Israel and around the world, (for a few examples, ISIS in Iraq, al Qaeda, Boko Haram, the Syrian and Libyan civil wars, the 9-11 bombings, the Boston Marathon bombing and the long list of Islamist terrorist events), are evidence of the world-wide threat of Islamism to western civilization, and we should begin treating it that way.
It is war, and not one that we have chosen, but one in which western civilization must choose to defend itself or face obliteration. Like George S. Patton said : "No bastard ever won a war by dying for his country. He won it by making the other poor dumb bastard die for his country."
And let me ask this: Do not the Palestinian civilians have any responsibility for the fact that they have an Islamist terrorist government? The Germans certainly held a degree of responsibility for the rise of Nazism, as did the Italians and Japanese for their governments.