In the same way that conservatives are animated by xenophobia and racism, liberals are animated by condescension and pride.

You see this in the way that urban dwellers often look down on country folk as dumb hicks. They're backwards savages who vote for the red team instead of enlightened intellectuals. It also helps to justify their atrocities without outright racism. By reducing Palestinian lives to a number and framing it as a tough decision, they can justify war crimes and still feel good. They view themselves as the smart intellectuals making hard decisions because the dumb rabble can't.