From the article:
An argument sometimes cited by critics of immigration is that migrants might taint their new homes with a residue of the culture of their countries of origin. If they come in great enough numbers, this argument runs, the accumulated toxins could undermine the institutions that make high incomes possible, leaving everyone worse off. Michael Anton, a national-security adviser to Donald Trump, for example, has warned that the culture of “third-world foreigners” is antithetical to the liberal, Western values that support high incomes and a high quality of life.
This argument, too, fails to convince. At times in history Catholics and Jews faced similar slurs, which in hindsight look simply absurd. Research published last year by Michael Clemens and Lant Pritchett of the Centre for Global Development, a think-tank, found that migration rules tend to be far more restrictive than is justified by worries about the “contagion” of low productivity.
So the theory amounts to an attempt to provide an economic basis for a cultural prejudice: what may be a natural human proclivity to feel more comfortable surrounded by people who look and talk the same, and to be disconcerted by rapid change and the unfamiliar. But like other human tendencies, this is vulnerable to principled campaigns for change. Americans and Europeans are not more deserving of high incomes than Ethiopians or Haitians. And the discomfort some feel at the strange dress or speech of a passer-by does not remotely justify trillions in economic losses foisted on the world’s poorest people. No one should be timid about saying so, loud and clear.