He/she doesn't. SW developers are not poor anywhere in the World. And what he says is not "don't enable jobs for non-US citizens, because I hate them", he says "..., because we will earn less money". It's a completely different motivation.

So the right question would be:

"Why do you oppose hiring devs (who are upper-middle everywhere in the world) elsewhere?"

And the answer is obviously: "Because it will push salaries down."

Personally, I think it's normal. SW development will be done remotely more and more in the future. Those, who want to build a moat, should probably focus on HW or firmware development.