It's not a new idea to me. It's an idea I've encountered many times, often propping up arguments of various kinds against pluralistic societies - which is an argument implicit in the comment above. Those arguments lead directly to ideas around ethnonationalism and segregating societies by cultural background, which is a direct analog for ethnicity.

There's a straight line between that argument - which again, almost always gets through around with out any kind of citations or research support - and ethnic cleansing. It's directly attached to racist ideas. Similar to social darwinism, it's something that seems like relatively harmless common sense on the surface, but leads to horrific implications when followed to its logical conclusion.

Interesting. So you don't actually argue that it's untrue.

You just argue that people shouldn't acknowledge it because doing so would lead to policies you think would be immoral.

I'm just not sure that this anti-truth stance is tenable or really worth it. What if we can acknowledge the facts and then... handle them in a non-evil way?

Or perhaps even use that knowledge to head off terrible outcomes that might otherwise happen? E.g. Lebanon-style ethnic civil wars.

I generally think that knowing the truth is useful and equips you to do good things. You just need a non-childish moral system to integrate it (too easy to feel moral if you just wish away the hard facts of the universe).

No, I argued that it's the sort of thing people assume is "common sense" when it is often very poorly supported. And my argument was that said assumption often comes from a bad place (when you examine it) and leads to a bad place.