Nationalism is the only rational mentality for long term sustainability.
A people should never be ruled by those who have no blood in the soil or by those who don't serve the needs of that people.
Nationalism is what makes great nations. You can forget about that for a while and play the game of the inevitable failure of multiculturalism, but it will always fail, you will always destroy society, and from the ashes, a cohesive, homogeneous people will reemerge to build back from the ashes of your stupidity as has always been done