Very complicated indeed, especially when considering the social cost of openly deviating from the orthodoxy.
I wouldn't caractérise this post as controversial; it's honest, and well argued.
DHH is spot on here, and I couldn't agree more. In-group preferences are real, normal, and healthy. I see parallels with Dawkins' "Selfish Gene" theory.

But don’t you for a second think this unity isn’t contingent on the homogeneity of ethnicity, values, norms, and perhaps even religion.