This article does a good job of listing some of the common counter-arguments: "1) Mass migration would create mass poverty. A popular one is that everyone from

This article does a good job of listing some of the common counter-arguments: "1) Mass migration would create mass poverty. A popular one is that everyone from South America and Africa would move to the U.S., which would, in turn, become a poor country. 2) No developed nation would be able to afford the new demand for their welfare programs. How would they keep a quality health system or unemployment protection program in place? 3) Terrorism. 4) The receiving countries would risk losing their national culture." But then it doesn't seem to address any of them! It just points people to an Amazon link to buy a book on the subject. Frankly, seems like pretty thin content marketing for this website.