I do love how the author, and others, basically assumed it was automatically talking about blacks. Plenty of whites, Latinos, Asians, etc are in Section 8 housing as well.
Around here, the problem is quite simple. If the folks who give a *expletive deleted*it leave and only people who don't give a *expletive deleted*it stay, you end up with a spreading problem. Part of Lancaster, PA turned ghetto from a single Section 8 housing project. Folks moved away from Water St, which made buildings nearby cheap, which Section 8 tenants moved into. Folks near the former projects tenants moved out. Repeat. It spread. You can see amazing old buildings in sections of Lancaster that look like they were shelled and then inhabited by refugees. Same thing happened in Coatesville. Near the entire town moved out, except for people that couldn't afford to do so.
That is how middle class Americans deal with crime and poverty, they move away from it. That is why property, class and culture become so linked to geographical zones.