Imagine that the Palestinians are unquestionably right. Imagine they lived in this land for a thousand years, and that they drained the lowlands and converted them to gardens. Imagine they welcomed Jewish refugees and let them live freely here. Would that have changed anything? Jews would still need a state of their own and would need to expel the friendly Palestinians who by the very virtue of their numbers undermine Jewish sovereignty.
The Torah sanctions genocide of Palestinians. In Deut2:32-34, Moses praises Israel for killing everyone in the region of Sihon, including the women and children. Like other nations in the Land of Israel, Sihon was not to be exterminated, but evicted. That option expired when Sihon went out to fight the Hebrews.

His action was not a sin against God because God had hardened Sihon’s heart (2:30), as he did with Pharaoh and apparently with the Germans. Sihon has sinned previously, thus the hardening of his heart was a punishment, and the subsequent defeat only a logical consequence of the punishment. In modern terms, punishment consists in sentencing the accused to death, and the injection of a lethal poison is just a consequence of sentencing.

Sihon threatened Jews. Presumably, he would have no pity on us, and we have acted in a quid pro quo manner.

Normally, the side that initiates hostilities—as the Jews did—is deemed wrong, and the other side merely reestablishes the status quo by fighting it. There is no right of quid pro quo on the part of aggressor. It was different with Jews, whether in the case of Sihon or the Palestinians. Our attack on Sihon was not wrong as other aggressions are, but morally neutral. We had no ill will against Sihon. We did not choose to attack him, but merely realized God’s will. We acted as instruments rather than individuals with free-will (and ill-will). To condemn us is the same as condemning a battle horse or a sword.