Nationalism is built on a foundation of "othering."

"Politically speaking, tribal nationalism [patriotism] always insists that its own people are surrounded by 'a world of enemies' - 'one against all' - and that a fundamental difference exists between this people and all others. It claims its people to be unique, individual, incompatible with all others, and denies theoretically the very possibility of a common mankind long before it is used to destroy the humanity of man."; -Hannah Arendt