What if, when the first middle-class black family or two had moved into Austin, NO ONE had panicked and sold. Wouldn't that have kept the neighborhood safe? An underclass family can't buy a house if the house isn't for sale! It seems as if the neighbors Steve commends as more practical/realistic/conservative were actually selling out the neighborhood both literally and metaphorically. If they had stayed put, there would have been no houses for anyone (white or black, middle-class or underclass, law-abiding or criminal) to buy, and the original families could have lived there indefinitely.
There's no end to the way that nice things are nicer than not nice things.