I simply do not think "middleman minorities" are credible analogies, since across the board in the middleman minority literature, they are not at the bottom of the social hierarchy, which is why they can perform the economic functions they do. As the paper I linked to in my last response details, European immigrants were able to gain solidarity with more native-born Whites precisely in their agreement that Black people represented the bottom of the social hierarchy. Aside from this, there are lots of other historical problems with Sowell's book that are better detailed by James B. Stewart's review I linked in my original article.

I've read Wilkerson's book, of course. It's magnificent, but it isn't going to give you the empirical history necessary to explain the phenomena we're talking about. There's a mountain of scholarship about this period. "The Origins of the Urban Crisis," just about anything by William Julius Wilson, Leah Boustan's "Competition in the Promised Land"—all of them provide massive reasons to doubt the simplified story that it was a bunch of people with a bad culture that welfare encouraged. As for your deindustrialization claim—you can put it as starting in 1970 if all you mean by that is globalization of industry, but i) even then, that's less than one generation into the second and larger migration and ii) this ignores capital flight from the city centers (where most Black migrants had moved to) toward suburbs and smaller towns in the United States, which happened as early as 1950—see especially "Origins of the Urban Crisis" on that point.