Your huddled masses yearning to breathe free. Photo: Orlando Sierra/AFP/Getty Images

President Trump threatened Thursday to send the U.S. military to America’s southern border, in order to stop a caravan of more than 2,000 Central American migrants from exercising their legal right to seek asylum in the United States.

“I am watching the Democrat Party led (because they want Open Borders and existing weak laws) assault on our country by Guatemala, Honduras and El Salvador, whose leaders are doing little to stop this large flow of people, INCLUDING MANY CRIMINALS, from entering Mexico to U.S,” the leader of the free world tweeted. “In addition to stopping all payments to these countries, which seem to have almost no control over their population, I must, in the strongest of terms, ask Mexico to stop this onslaught - and if unable to do so I will call up the U.S. Military and CLOSE OUR SOUTHERN BORDER!”

There are reasonable arguments for reforming American immigration law, so that asylum seekers are not incentivized to make long, dangerous treks up the North American continent to press their claims in the United States. And it is also true that previous migrant flows have already exhausted our government’s resources for detaining asylum-seekers and processing their claims (although, this is partly because the Trump administration refuses to expand alternatives to mass detention, largely out of a principled commitment to treating migrants with wanton cruelty).

Nevertheless, it’s hard to make a rational case for why our government should regard Central American migrants as a threat to the safety and material well-being of the American people.

Contra Trump, there is no basis for believing that undocumented immigrants or asylum seekers are predisposed to criminal activity. In fact, we have long known that native-born Americans commit violent crimes at far higher rates than either legal or undocumented immigrants. And newer research into immigration and criminality has proven even more devastating to the nativists’ case: States with higher concentrations of undocumented immigrants tend to have lower rates of violent crime — and this correlation persists even when controlling for a given state’s median age, level of urbanization, and rate of unemployment or incarceration.

While there’s little basis for believing that Central American migrants have brought crime and lawlessness to our country, there’s good reason to think that we brought such conditions to theirs. After all, it was the CIA that overthrew the democratically elected government of Guatemala in 1954, and thereby subjected its people to decades of dictatorship and civil war. It was the streets and prisons of California that gave birth to MS-13, and American immigration authorities that deported that gang back to El Salvador. And it is America’s taste for narcotics that sustains the drug trade in Honduras — and our war on drugs that ensures such trade is conducted by immensely profitable and violent cartels. One can debate what, precisely, America owes the people of Central America in light of this history. But allowing the region’s most desperate people to assert their right to seek asylum — without kidnapping their children — seems safely in “the least we can do” territory.

Separately, the American economy is actually in great need of young, unskilled workers (like many of those currently marching toward the southern border). On the Labor Department’s list of the 15 occupations that will experience the fastest growth over the next six years, eight require no advanced education. And with the baby-boomers retiring — and birth rates plummeting — the future of American economic growth depends on an infusion of foreign labor. It is true that there is some basis for believing that mass, low-skill immigration depresses the wages of native-born high-school dropouts (although that claim is contentious). But there is no basis for believing that restricting immigration will do more to boost such workers’ take-home pay than encouraging unionization through labor-law reform, or expanding the Earned Income Tax Credit (EITC), or a host of other progressive policies that Donald Trump vehemently opposes.

All this said, there is abundant evidence that a significant portion of the American electorate finds the idea of large masses of brown-skinned people crossing the U.S. border to be psychologically threatening. And there is also social science research suggesting that, when the median white voter is primed to contemplate rapid demographic change, her political views become more conservative, even on issues unrelated to immigration. Thus, the story of an invasion by Central American hordes — egged on by Democrats, and vigorously opposed by Republicans — might well be a politically convenient fiction for our president.