And by encouraging segregation. Racial tensions are like diesel fuel for their political engine.
The issue is not actually race. The races get along quite well in suburbia, and blacks are successful there. Black immigrants are successful at rates that far outpace non-immigrant urbanites.
The issue is big city urban culture that encourages people to behave in ways that lead others not to want to hire them. Suburbanites (black or white, there is no difference) generally encourage their kids to behave in employable ways, and to work hard to obtain the most profitable employment they can. Urbanites often do not do this...and some ruralites as well...which puts them at a disadvantage.
The difference is american-sub-cultural, not racial. Blacks can easily succeed in America; urbanites often have a harder time.
The good news is that once behavior changes, prosperity comes.