It has only been demonised because WW1 and WW2 was blamed on nationalism and is now associated with racism and xenophobia in the late 20th and early 21st century.
Actually, nationalism was a reaction against imperialism.
WW1 occurred because the Austrian Empire was weakening and breaking up. Understandably, when this was happening, peoples that used to be under the Austrian Empire aspired to become independent, and that was why the Serbian terrorist assassinated Archduke Franz Ferdinand.
Woodrow Wilson's 14 Points after WW1 articulated and affirmed the principles of national self-determination, which described the principles of nationhood.
WW2 occurred because Britain and France - both empires - wanted to contain Germany's imperial ambitions.
America is an empire, the EU is an empire, Islamic State wants to become a nation state and then an empire with global domination in mind, but Western nations just want their country back again from whoever is pulling the strings of their leaders who keep foisting more and more immigration on a weary and increasingly anxious populace.
Nationalism does not have to mean war, any more than looking after your own interests must mean you will always be fighting and killing other people, if you are not a gangster.
In reality, well-led nations use a mixture of war and diplomacy as an instrument of policy. We just want wise leaders leading our respective nations, and for this to be done, we have to reform our political process.
Nationhood is indispensable because there seems no other way of organising human society. A nation is a piece of territory with borders with its own government. It is the only group we can join that is small enough to care, but big enough to matter.
The real controversy is not that nation states should exist, but how they should be run, who should participate in their decision-making processes and what rules they should follow. The real controversy is therefore between patriarchy and matriarchy ie whether we return to social conservatism and the practice of marriage as a means of reviving the patriarchy run on the clear rules of healthy competition and low taxes, or carry on as we are, being a degenerate matriarchy in which the preferences of immoral women are always prioritised in an environment of indiscriminate universal suffrage, where men are lower in status to women.
It is precisely because the West is a matriarchy that makes us a post-truth society operating post-truth politics. Because we are no longer moved by facts and logic, we will be moved by something worse: threats, intimidation and violence.
It is a shame no one will discuss this.