This means that Israel is the aggressor in this conflict, and the Palestinians fight in self-defense. Under these circumstances, Israel's right of self-defense cannot justify Israeli violence. Israel is certainly entitled to protect its citizens by evacuation and other non-violent measures, but it is not entitled to harm a hair on the head of a Palestinian firing rockets into Israeli cities, whether or not these rockets kill innocent civilians.
Self-defense gives you the right to resist attacks by any means necessary, and therefore, certainly, by the only means available. The Palestinians don't have the option of using violence which hits only military targets - apparently even the Israelis, with all their intelligence data and all their technological might, don't have that option! But suppose a bunch of thugs install themselves, with their families, all around your farm. They have taken most of your land and resources; they're out for more. If this keeps up, you will starve, perhaps die. They are armed to the teeth and abundantly willing to use those arms. The only way you can defend yourself is to make them pay as heavy a price as possible for their siege and their constant encroachment on your living space. You're critically low on food and medical supplies, and the thugs cut off those supplies whenever they please. What's more, the only weapons available to you are indiscriminate, and will harm their families as well as the thugs themselves. You can use those weapons, even knowing they will kill innocents. You don't have to let the thugs destroy you, thereby sacrificing your innocents (including yourself) to spare theirs. Since innocents are under mortal threat in either case, you needn't prefer the attackers' to your own.