The history of housing discrimination in the US would challenge the notion that a middle class suburb would not push out minorities. This practice was rampant in the period after WW2 and continued into the 70s and 80s. It has little to do with notional affordability.
Interesting. I suppose that could have some effect, but I was not even born until housing discrimination was over with and when I moved into my small town it was largely farmland and not much of a suburb until a decade later.
Further, if housing discrimination was still going on in the 90's and 00's, I have no idea where these people were being "pushed out" to. The closest towns/cities with significant racial minority populations were at least 250 miles away...the city I grew up outside of was 90% white (currently 82% white) and there were/are plenty of undesirable locations there. It's middle America, there are just a ton of white people (sorry?).
https://en.wikipedia.org/wiki/Redlining