Business people do this all the time. Marketing managers are paid to do it. All the years I was at National Review there was a slight but noticeable undercurrent of anxiety about the readership being too old. These anxieties are perfectly normal in any business environment.
As soon as I get to thinking that our race hysteria couldn't possibly get any more unhinged than it is, something like this shows up to prove me wrong.
Of course not many nonblacks feel comfortable in a crowd of blacks. We know how volatile blacks can be; and we know that in any black crowd there will be some who hate nonblacks, and will be ready with insults and provocations.
We see evidence of this daily. (Here is today's. Can someone please tell me what language is being spoken by the lady doing the recording?) Why do people pretend to be shocked when someone says it out loud?
Isegoria's first commenter is right, I think, that what Levenson says about Southern whites applies a fortiori to Northerners. The rule I heard from a black co-worker when I first came to the states is: "In the South you can get as close as you like, but don't get too big. In the North you can get as big as you like, but don't get too close."
Isegoria's second commenter has interesting things to say, too; although whether they are true or not, I don't know.