Something needs to define a nation. I simply agree to that one point he made that there should be a dominant culture. *shrug*
But the proportion of racist white nationalists in the US is tiny, so maybe you all can start a lil' country and call it Trollia. And we are defined as a multicultural nation. Saying it ends up in tribalism, ethnic conflict and it will destroy itself is white nationalist anti-American fear mongering. The rise of authoritarianism in this country is a sick disease.
Ah, but the ones saying multiculturalism will end up in tribalism, ethnic conflict and it will destroy itself are racist white nationalists who are currently arming themselves for the race war. That doesn't bother you.