Nationalism is like rats in New York; always have been there and always will be. But not always equally numerous.
As now we see nationalism getting more popular, the right approach is not in arguing that nationalism is bad, what Mr. Parry does in this essay. Similarly, as it with rats in New York, one needs to ask why we have more nationalists now than before.
As a historian, Mr. Perry should be well equipped to give us an answer. Maybe in his next essay.