Cheeky, but isn't nationalism/patriotism just rational self interest? Why wouldn't I want the system I pay taxes into to put me and other people in this boat first?
I like this definition, personally:
“Patriotism is supporting your country all the time and your government when it deserves it.”
― Mark Twain
It is rational self interest, but self interest beyond a point is selfish, which is generally considered a negative personality trait.
If you want to put it in game theory perspective, normalizing selfish behavior means that when you could benefit from something in another country but won’t you’ll be the one suffering discrimination.
If we can reach agreements international cooperation can benefit all parties better than the greedy solution.
