I don't think it is a weak argument.
Plainly blacks DO have it much better here than in, say, Nigeria, which is perhaps the least awful of African "states," but it is a morass of organized kidnappings by the thousands, corruption, poverty, separatism in the South, jihadism in the North, essentially a failed state now, according to the WSJ.
The reason blacks have it better here is because of white rules, laws, police, the order we bring that make a civilized society possible for us, and at least a better one for them. Take zoning laws and housing codes: in Jamaica blacks live in cardboard shacks propped up against each other, dirt floors, no toilets. Same in most of Africa. We don't allow that kind of housing, so the slum landlords that rent to blacks have to do better than that; otherwise they wouldn't.
Whites prop blacks up to a higher standard of living than they could do on their own: and how do I know that? Because outside of white laws, they do much, much worse.