You're saying a black person who grows up in a white subculture then is less at risk of poverty? I call bullshit on that.
It doesn't matter what subculture you grew up in or are exposed to. It is what other people perceive of you that influences the likelihood of you falling into poverty. Skin color has a lot to do with that. Maybe the reason black people don't appreciate the idea of hard work is because no matter how hard they work, they don't come up ahead?
By subscribing to the idea of these subcultures being responsible for work ethic, you're still placing work ethic innate to the race - and that's flat out racist.
And for the matter of preconceived biases, I'm not the person coming into this suggesting that certain cultures have work ethic issues.