So What if Just War is Impossible?

From time to time one hears the following apologia for various Palestinian war crimes (this is one example, but it's decently representative):

Based on the fact that the West Bank and Gaza are occupied territories that are economically and politically controlled by Israel – and where there is no freedom for its residents – I believe they have the absolute right to fight for that freedom. I personally do not think Hamas’s rockets are a productive strategy of resistance, but it still has the right to respond in such a manner – as does any liberation movement against colonialism.
[...]
The argument that Hamas is using human shields has no weight. There is no evidence that this is actually occurring en masse. Gaza is tiny – about the size of the Cape Flats. It is one of the most densely populated places on the planet. There is no place where Hamas could stockpile arms away from a population centre.

This argument, in essence, is that Palestinians have a "right to fight" against Israel, and since the only way that they can functionally exercise that right is by indiscriminate rocket fire and by intermingling their fighters within the Palestinian civilian population, those activities are acceptable.

This is, of course, nonsense. The laws of war do not contain an exception for when following them means one's preferred side won't win. The laws of war are, by design, indifferent as to which side "should" win, operating off the reasonable presumption that each side in any armed conflict will think itself just and therefore view itself as exempt from the strictures of the laws of war. This is why we largely no longer adopt the Augustinian approach to just war theory. The point being, if you can't win a war while obeying the laws of war, then don't fight it. There is no right to win an armed conflict.

But here's the thing -- this cuts both ways. One also often hears defenses of Israeli strikes which have crippling civilian casualties on the grounds that, well, Hamas uses human shields and stockpiles its weaponry in civilian areas. Quite true! But that is not carte blanche authority for Israel to do whatever it will. There are valid questions over who should be considered responsible for civilian casualties when Party A strikes Party B's military targets embedded in a civilian population -- if for no other reason than to deprive B the incentive to do just that. Nonetheless, it cannot be the case that infinite civilian casualties are justified simply because of B's (admitted) legal violation. Considerations of proportionality need to come into play. And if that limits Israel's ability to effectively prosecute a war on Hamas -- well, the laws of war don't guarantee you get to win a war.