The threat model is "been indoctrinated by years of propaganda to be fearful of a vague nebulous threat of being around people who don't look and act like me"
It was not great to watch, but it was great to let my parents know who exactly they should stop associating with.
They do. But it's not a law of nature; it's a conscious decision, by people who should know better, to start lowballing real estate and salaries when they notice "too many" lower-income or black (of any income level, including high) people around.
You don't want to call it a concerted effort, but then you look up, say, the distribution of Whole Foods stores in the National Capital Region, and start to wonder.