"Intentional mass murdering of civilians" is what Palestine did to start this war in the first place. So even if Israel were deliberately targeting civilians (there's no evidence for this) they would still be on the right side of this conflict.
Last times this happen in europe were: 1) WW2, 2) The massacres in the Yogoslavian wars, and especially in Sebrenica which was a clear ethnic cleansning/genocide and the war leaders ended up getting convicted for war crimes and crimes against the humanity.
Benjamin Netanyahu is on the way to become the next Milosevic, a war criminal.