Even on its own terms, your analogy doesn't make sense.
Palestine is a colony of Israel. The movement for national liberation there includes various reactionary forces, yes. And yes, we would support Palestinian independence even if it was under an Islamist or reactionary-nationalist government.
Russia is not a colony of Ukraine. Something closer to the reverse is the case. In what sense does Russian nationalism - including the far-right, quasi-fascist, racist Russian nationalism of many of the key figures in this initiative - have any objectively progressive characteristics or potential? Russia is one of the world's biggest imperialist powers. In what possible sense can Russian nationalism be anything other than wholly reactionary?