When you say "mass murder," I assume you are referring to the war that has resulted in 40,000 casualties (at least, according to Hamas). Of those deaths, we don't know how many people were combatants. Does Israel have a right to kill Hamas fighters, or is that also mass murder? This is the problem with tossing around terms casually when analyzing something of such import. This is the POINT of the jurisprudence -- so that warfare is not confused with genocide.

You're upset about the war. It's horrifying. But the solution is not to simply change the meaning of legal concepts to fit your narrative.