"Why wouldn’t a nationalist, eager to subordinate and sacrifice individuals within his own nation to the collective, not be eager to do the same to outsiders?"
Well said, mate. Allowing these hotbeds of tribalism to develop in parallel would create a world of countries that otherise and hate one another. If "universal truth" does not exist, then each of those countries could claim that they possess "Aryan logic" or some other noxious derivative, which means that each country would be inaccessible to one another. The logical consequence of this would be imperialism.
Nationalism vs. freedom - Aristotle's Golden Mean is valuable here.
As I like to say, nationalism is like nitroglycerine: it can either blow up bridges or heal hearts.
"Why wouldn’t a nationalist, eager to subordinate and sacrifice individuals within his own nation to the collective, not be eager to do the same to outsiders?"
Well said, mate. Allowing these hotbeds of tribalism to develop in parallel would create a world of countries that otherise and hate one another. If "universal truth" does not exist, then each of those countries could claim that they possess "Aryan logic" or some other noxious derivative, which means that each country would be inaccessible to one another. The logical consequence of this would be imperialism.