How Much Homogeneity Does Society Need?

It feels strange writing about this topic, some 25 years after I had it completely settled in my mind. But nothing is ever really settled, I suppose. The claim that I had long ago concluded was a basic historical and economic fallacy is back in a big way. The claim is that society needs homogeneity to be orderly and free. It is a core claim of the alt-right and its sympathizers (and, in a different way, of the alt-left). It is what leads them to reject freedom as a path forward and embrace state control of demographics.