I think history gets recursive really quickly. After all, historical narratives produce human action that then produces new historical narratives which lead to new actions. White supremacy is deeply rooted in this self-reinforcing process.
The Nazis in particular were obsessed with history, using linguistic and archeological research extensively to justify their actions. The ancient "Aryans" had proved their superiority by dominating the pre-Indo-European culture, which justifies the subjugation and genocide of human beings all over the globe, including Africa and the Americas. Lebensraum in Eastern Europe is not too big a leap from Manifest Destiny in the Western United States, both of which contribute to the modern white supremacist's belief that settler-colonial states like the United States or Australia ought to be whites-only.
Narratives of resistance also depend a lot on history. Indigenous rights movements are very rarely framed in terms of current conditions. Instead, the focus is on historical claims about land, cultural heritage, and injustice. I have a lot of trouble wrapping my head around this stuff. I support land back and other projects to bring power and autonomy back to indigenous people, but I think that comes from a sort of universalist understanding of human rights rather than a fundamental belief that indigenous nations have unconditional sovereignty over tracts of land they claim to own for historical reasons.
I don't know of any indigenous organization ever asking for anything beyond basic self-determination and restitution. However, there was one semi-popular (white) leftist Youtuber who argued it would be perfectly just for indigenous people to force all colonizers and their descendants into camps, where they may either participate in anti-American education or be deported. This is extreme, but it's not too far off from being a consistent application of principles of sovereignty the United States applies to itself.
I myself have not developed a view on what it means to legitimately own land. According to https://native-land.ca/ my house sits on land owned by the Ute, Sioux, and Cheyenne nations. Does that mean organizations belonging to these nations have a right to levy rent/taxes and evict me if I fail to pay? Can they reasonably require I take a test on their history and culture and deport me if I don't pass? If they decide to build something in my backyard and I resist, do they have a right to force me to comply?
If owning land is like owning a home, you'd expect certain rights to be associated with it. A homeowner has a right to ask any guest to leave at any time for any reason. No one besides the homeowner may modify or even access any part of the home without permission. If someone breaks in or obstinately refuses to comply with these rights, it's acceptable for the homeowner to use a reasonable amount of force in response.
I don't think this is entirely theoretical. It has major implications for leftist movements, and I don't think enough effort is being put into properly fleshing out and interrogating these issues. If the non-indigenous are just guests on indigenous land, do indigenous people get veto power over any democratic decision made within their historical territory? Should we build special institutions and chapters within leftist organizations that guarantee defined privileges for members of indigenous nations? Whenever there's a disagreement between a guest and a host, should we take the host's side by default?
I have not heard of The Swerve; maybe I'll check it out. This reminds me of a discussion The Amazing Atheist had on Kyle Kulinski's show about nihilism. It does seem strictly true that there is no way to objectively determine meaning or morality. Even if there is a god, there's no inherent reason we should uncritically accept its values as true.
The Amazing Atheist argued that he believes in nihilism in part because people constantly fail to live up to their own moral standards. I feel that this actually points in the opposite direction: Why the hell would people develop moral systems they could never dream of living up to? Even if I can't justify it logically, I do live my life as if there is an objective morality that exists outside of myself. I do eat meat, but I've also been convinced through argumentation that veganism is the ethically superior position. Veganism is completely irrational in the sense of maximizing self-interest or even species interest, but it's managing to spread all over the world just the same. When I spent two months in Egypt and met people from literally all over the world, what shocked me the most was how similar everybody was. Even if it's not justifiable, I can't shake this intuition that some sort of universal value exists.
I am becoming more and more concerned with how identity politics is affecting the left. People are watching how the left constantly purges itself and devolves into bitter arguments over slight differences in opinion, and they're deciding they want none of that. I think the backlash we're seeing right now has a reasonable side to it. I don't want to live in a society where I'm not allowed to be wrong and I'm constantly agonizing over what people think of me. I've seen leftist organizations that do amazing work but are borderline dysfunctional because they're constantly getting into arguments, assuming the worst from their colleagues, and dog-piling on people. I don't know what it looks like from the outside, but I'm very happy that this trend is still small enough that I can leave and spend time outside of it. The left is going to need to learn how to live and build healthy communities together before acquiring more power.
I might have to look more into Kendi and other academic anti-racist stuff. People I usually trust have said that Critical Race Theory is basically just looking at stuff critically through the lens of race, but deeper dive videos I've watched paint it out to be much less agreeable. Israel is a pretty good piece of evidence that leftist identity politics isn't just a naive attempt to create a new hierarchy/aristocracy based around oppression, as the right often posits. As you say, if there were an oppression olympics, the Jewish people would clearly have a winning ticket, but that doesn't give them license to engage in settler colonialism and apartheid.
The question that comes up for me is how this affects the framework we have for Native Americans. Are Israelis seen as less indigenous than the Palestinians because of their long diaspora and thus have no legitimate claim to the land, or is there a fundamental set of principles that make these actions unacceptable regardless of the identities and historical claims of those involved?