Earlier quoted context omitted.
For a migratory species it is literally inhuman to erect a border. Borders should be jurisdictional boundaries but should be permeable like the states in the US. The rest of the tribalism BS is just that.
Humans stopped being migratory about 12,000 years ago. You probably don't want criminals to freely move into your country. You probably want a country that gets funded by taxes (both short term and long term). No country in the world maintains open borders. Everytime there has been mass unorganized migration it has been a humanitarian disaster. Platitudes only work on paper.
Also, you're incorrectly conflating mass migration with open borders. You can have open borders without causing a mass migration and vice versa.