You said that Israel is justified in their war on Palestine. If no amount of collateral damage is acceptable, they would be no longer justified after the first civilians were killed, so you obviously do consider some amount of collateral damage as acceptable.
So I’ll repeat my question: what is the percentage of the Palestine civilian population that has to be killed before Israel is no longer justified in their war? You can answer the question, or you can not do so. The implications of either option are hopefully clear to you.