Diversity is the hallmark of empires, not democracies.
Woodrow Wilson was wrong about many things, but he was a veritable hedgehog about One Big Thing: the principle of national self-determination. When it came to his dream of the League of Nations, Wilson was a utopian romantic; but on the question of how to draw national political boundaries, he was a Founding Father of what may be called National Realism.
National Realism comprehends and respects the perhaps tragic, but nevertheless undeniable, fact that most people are deeply attached to collective identities and aspirations. It accepts as both natural and important that psychological well-being would be rooted in a terroir, a set of traditions or other mythologies about who people are and where they come from, that can serve as a source of meaning and self-understanding, as well as social cohesion. It acknowledges that nationalism is a fixture of modern social and political reality.