Ethno-nationalism is good and permitted by God. The apostle Paul speaks to the Romans about his own ethno-nationalism. He tells them he was willing to be anathema from Christ for his own people & nation (Jews), if it meant not offending God resulting in the anathema. You can't get any more ethno-nationalism than that example.
Romans 9:3-5 (Douay-Rheims)
For I wished myself to be an anathema from Christ, for my brethren, who are my kinsmen according to the flesh,  Who are Israelites, to whom belongeth the adoption as of children, and the glory, and the testament, and the giving of the law, and the service of God, and the promises:  Whose are the fathers, and of whom is Christ, according to the flesh, who is over all things, God blessed for ever. Amen.
 "Anathema": A curse. The apostle's concern and love for his countrymen the Jews was so great, that he was willing to suffer even an anathema, or curse, for their sake; or any evil that could come upon him, without his offending God.