It is Hamas' choice use the Palestinian populace as human shields, and supposedly civilian locales like hospitals and schools as rocket staging areas, weapons chaches, and entrances to tunnels for terrorist attacks-- knowing that doing so makes such locations military targets, and knowing such use of civilians will inevitably increase collateral casualties.
Call it "guerrilla warfare" if it makes you feel better, but it's just nicer language for "terrorism."
Israel warns civilians to leave threatened areas, and to avoid Hamas staging areas. It phones ahead of attacks, it sends texts, it drops leaflets, it broadcasts on the radio. Hamas, by contrast tells the Palestinian populace to avoid Israeli warnings, and to go stand in the line of fire.
Given that it is ridiculous to suppose that Israel should not defend itself and retaliate from strikes, it is doing more to try and avoid civilian casualties than any army in modern history has ever done, and more than the laws of war require.
No one takes pleasure in the deaths of Palestinian civilians-- except perhaps a few lunatics on the extreme right wing-- but civilian casualties are an inevitability in war. If they were going to be truly avoided in Gaza, Hamas should not start wars and should give up terrorism.