There seems to be a newfound fervor among stalwart opponents of traditional Christian religion for the Bible's teachings on treating the stranger with dignity and respect. 'Tis less a religious revival than a base opportunism which leads them to search the Scriptures, but so be it! God can turn even base incentives to his own purposes.
There is no controversy over the fact that Christ enjoins his followers to show hospitality and kindness to outsiders. The parable of the Good Samaritan demonstrates this amply enough.
Some attempt to leap from this simple fact to a definitive conclusion regarding how a state should police its borders or enact immigration policy, but this is prima facie absurd. For Christians, the state should ideally be informed and guided by the Church and her Scriptures in the construction of policy. But the state is not reducible to the Church and she is charged with duties that the Church must not undertake (punishment of criminals, waging of war, etc.), just as the reverse is true (administering of sacraments, preaching, etc.)
Perhaps recognizing this fact, Carl Schmitt distinguished between a private and political enemy, a distinction he locates a basis for in Latin and Greek:
The enemy is hostis, not inimicus in the broader sense; πολέμιος, not ἐχθρός. As German and other languages do not distinguish between the private and political enemy, many misconceptions and falsifications are possible. The often quoted “Love your enemies” (Matt. 5:44; Luke 6:27) reads “diligite inimicos vestros," ἀγαπᾶτε τοὺς ἐχθροὺς ὑμῶν, and not diligite hostes vestros. No mention is made of the political enemy. Never in the thousand-year struggle between Christians and Moslems did it occur to a Christian to surrender rather than defend Europe out of love toward the Saracens or Turks1
But that's Carl Schmitt. Far from an authority on Scripture and, however sound his argument, not one to likely ever be heard by those with cupped hands over ears shouting "Nazi!"—the slur being technically accurate for a change.
For a more reputable source we turn to a Saint who comes to a very similar conclusion from a slightly different angle:
In the Saracen encampment they asked Saint Cyril [Enlightener of the Slavs]: 'How can Christians wage war and at the same time keep Christ’s commandment to pray to God for their enemies?’ To this, St. Cyril replied: 'If two commandments were written in one law and given to men for fulfilling, which man would be a better follower of the law: The one who fulfilled one commandment or the one who fulfilled both?’ The Saracens replied: 'Undoubtedly, he who fulfills both commandments.' St. Cyril continued: 'Christ our God commands us to pray to God for those who persecute us and even do good to them, but He also said to us, Greater love hath no man than this, that a man lay down his life for his friends (John 15:13). That is why we bear the insults that our enemies cast at us individually and why we pray to God for them. However, as a society, we defend one another and lay down our lives, so that the enemy would not enslave our brethren, would not enslave their souls with their bodies, and would not destroy them in both body and soul.'2
The basic takeaway here being that, in the real world of daily life, there arise situations where duties seem to conflict. Sometimes we have to be prudent, prioritizing higher goods over lower, but as St. Cyril points out here, other times we can simply do two things at once. Love thy enemy isn't an injunction to national suicide in the face of a collective threat. It's an injunction, like "turn the other cheek", to bear personal insults and injury without retaliation and to even pray for your persecutor. This can be done while defending your nation against the Saracen. There is no conflict.
Of course, just how a Christian state (or a secular one that you want to influence in a Christian direction) should balance its duty to protect its citizens and the call to be hospitable is an open question which can't be foreclosed by scriptural exegesis. Whatever that answer is, it's not handed down from on high, though we can certainly look to saintly Kings and Queens for examples. But ultimately the ruling authorities of our own day must exercise prudence and wisdom in judgment, neglecting neither injunction. And there may be reasonable disagreements about whether they actually achieve this aim or not. The only absurd position—the one most prevalent among an hysterical segment of the "Christian Left" at the moment—is that the answer does lie in a facile, superficial exegesis of Scripture. One that allows no distinction between Church and state, personal and political, and indeed would reduce the former to the latter in both cases.
At a time when Trump is turning progressives into flag-waving constitutional originalists, and many conservatives into nationalists, he's also managed to convert much of the staunchly secularist, anti-theocratic Christian Left into avid theocrats. Look at that. And here we find a vindication of Schmitt who wouldn't be the least bit surprised that beneath the veneer of ideology and "principle" lurked the naked friend-enemy distinction, truly animating the political.