I think the following might be the reason:
While a lot of poor blacks are on welfare, those who actually work usually have jobs in the private sector. On the other hand, a huge majority of middle class blacks work in the public sector. Here is one example. My home city of Houston is approximately 25% black. Yet, more than three-quarters of the city bus drivers are black. Affirmative action is most strongly applied towards government jobs. Back in 1997, there was a local affirmative action initiative on the ballot. The voting results in the Chronicle showed that Riverside, a middle to upper-middle class black neighborhood, had the highest support for the initiative.
I live in Houston, too. Second-hand "as told to" anecdotal info is that both Metro, the bus service, and the Solid Waste Division are black fiefdoms.
The word is, they're color-blind on hiring, but if you're white and you hire on, the black hands will "unofficially" make sure you don't stick around.
In other words, they're racist as hell and nobody ever, ever, ever, in 30 years, has called them on it. Never.