I think it's a little far reaching to say an income requirement for a neighborhood is a racial prejudice. If the majority of people who make 2.5x the median are white, then there's another problem that needs to be addressed, and that's "why are black people making less money."

The article is saying new expensive suburbs force poor people to live together, which causes slums. While the practice is still discriminatory, it isn't actually racist. The people in the neighborhood who assume only white people can afford the area, now those people are technically the racists.

Incidentally, the answer to the question is at the bottom of the article:

A child who grows up in a high-poverty area is likely to be poor when he grows up. Research out this year from Harvard shows that children who moved from poor areas to more affluent areas had higher incomes and better educational achievements than those who stayed in poor areas. Without dramatic changes, today’s children who live in high-poverty areas are going to grow up to be poor, too.

Well, the whitewashing is just a symptom of the problem really. If minorities were poor, then they stayed poor, and will stay poor. I feel like the article is including the racial aspect where it doesn't need to be. Another article was linked that explains how section 8 is failing, and this is where the focus should have been.

As an anecdote, in my area nobody would want the "white trailer-trash" to move into their beautiful neighborhood (because they're poor), but there's plenty of racial diversity around here to imply that the decently paid Mexicans from the air force base are a welcome addition. The neighborhood is still predominately white, though, so I might just be crazy.