In my experience a lot of misunderstanding comes not from lack of facts, but a lack or difference in perspective. Hardly anyone even feels the need to justify their actions, let alone squeeze it into some bizarre cowboy metaphor.

Which aligns with what the studies seem to indicate. Often the strongest objections arise in a subject that we hold very dear as part of our identity.

What about people who think we need more binary thinking and fewer shades of gray? How do you even form a nuanced (gray) argument against that kind of dogmatism? Where do you draw the line against line-drawing without being hypocritical?

This isn't just rhetorical: this is a problem we're struggling with as a society. People are intellectually exhausted and are drawn to ideologies that answer their questions for them in a clear, unambiguous way. We're in an ideological arms race, becoming more polarized and less rational merely as a survival mechanism.

"Four legs good, two legs bad." is already past the point of no return and there is no "a society" as you quote but two battling for supremacy.

Historically we have little evidence of solutions other than civil wars.

Asking how to roll back identity politics without a physical war is like debating strategies to avoid nuclear war after the missiles have launched but before the mushroom clouds form. Its a little too late for that and there really isn't any point in wasting limited time in trying to roll back or blamestorming in circular firing squads.

You challenge their support. Continue to push them to draw more lines, until they've drawn so many lines that they're all alone inside their fence. Try to convince them that no one matches up to their worldview, not even their family and not even themselves.