You exaggerate the difference between the north and south in regards to race. You overestimate the tolerance of the south to Jews, or people with foreign accents, and you underestimate the discrimination against blacks in the north. Restrictions against selling to blacks were not unique to Chicago, they were largely universal. The NAR regarded introducing new ethnicities into a neighborhood as an ethics violation until 1968.
I get how he might underestimate the intolerance in the South, but I didn't get the sense he was doing so in the North? In fact, he seemed to be saying the North was MORE intolerant, in a lot of ways, then the South could be sometimes.
http://www.inman.com/2014/04/17/realtor-code-of-ethics-once-...
published in New York: https://en.wikipedia.org/wiki/The_Negro_Motorist_Green_Book