I am not addressing this specific point directly but I can say, being from the deep south with memories of the Jim Crow days that in Catholic areas African Americans were treated much better than in the  Protestant areas. Still are.

The Washington DC area (Georgetown)  was southern pre-Civil war. Slavery had a place for and could usually carry the marginal non-productive people before the welfare state. This issue is not as one-dimensional as you are lead to believe.