But the silliest argument is that somehow America is filled to the brim and just can’t comfortably fit any more people — you know, all that rush-hour traffic and those long lines at the airport. If so, then perhaps in addition to stopping immigration, Washington should also discourage parents from having too many children. Maybe a federal child tax instead of a child tax credit.

Of course America isn’t all filled up. It is one of the least population dense countries in the world. Moreover, there are plenty of other advanced economies where the inflow of immigrants as a share of the population is higher than the United States, and whose stock of immigrants as a share of the population is higher as well. Doubling or even tripling the current million a year in legal admissions would be a smart policy for a country facing an economic growth and fiscal challenge from an aging population and slowing labor force growth. Worried about the decline in startup businesses? Slowing population growth in the West, Southwest, and Southeast regions since the early 1980s appears to be a major factor.

But none of that matters if the real reason you want to limit immigration is because you either think any population growth anywhere is bad for the environment — which maybe Anton does since he is oddly worried about carbon emissions — or you are just plain uncomfortable with the cultural, ethnic, and racial change that immigration can bring.