I'm seeing this getting knocked around on Twitter a bit today, but it's worth discussing at greater length. Many American conservative intellectuals seem to me to be engaged in a peculiar kind of moral mathematics in order to develop an issue position that's congruent with the racist and xenophobic sentiments of many conservative base voters. This involves appealing to economist George Borjas' conclusion that immigration of low-skilled workers from Mexico reduces the wages of American high school dropouts.
One thing to flag here for later reference is that Borjas' conclusion is contested by other researchers.
But stipulating that Borjas is correct, what he says is that immigration of Mexican workers is great for Mexican workers. Borjas also says that immigration of Mexican workers raises average wages of American workers. But it lowers the wages of the ~12 percent of American adults who don't have a high school degree. The idea, apparently, is that we need to give strict priority to the interests of this minority of the American population. But why? It seems to me that in most contexts people in general—and conservatives in particular—tend to reject proposals to assist the underclass by immiserating the majority of Americans. To decide that the appropriate time to ask the median American to make this sacrifice is when doing so will also immiserate Mexican-born would-be immigrants is exceptionally odd. It seems to involve putting zero—or perhaps negative—weight on the interests of Mexican-born persons. But it's even worse than that, since the population of American workers includes many people who were born in Mexico and Mexico-born Americans are disproportionately likely to fall into the low-skill category!
Indeed, according to Heidi Sheirholz Mexican immigration raises the wages of the typical US-born high school dropout. So we're immiserating native-born Americans and potential immigrants from Mexico in order to give strict priority to the economic interests of foreign-born workers who've already immigrated to the United States. That strikes me as a rather contorted calculus.
And then there's the question of how confident we should be in Borjas' findings. Giovanni Peri's research says he's wrong and immigration raises wages across the board. Patricia Cortes says that when we look at prices and not just nominal wages, that immigration raises real wages. Jennifer Hunt says immigration raises high school graduation rates. I'm not going to promise that Borjas is wrong. Peri and Hunt and Cortes may be too optimistic. But given considerable uncertainty as to whether immigration restrictions would even succeed in helping US-born high school dropouts, it seems perverse to choose such a costly method of doing so.