> _It's just easier to be an immigrant or hyphenated-American in world class metro areas that can support a variety of ethnic and cultural clustering._
The fact that there aren't as many african-americans in the bay area (outside of a handful of locales), doesn't make the GP's point invalid.
I'm an immigrant in SF, and there are few places in the US where I would feel remotely as comfortable. Even being "white" (latin american of southern european ascent) I have a noticeable accent. That accent has triggered abuse by an elderly woman right after the past presidential elections in an ice cream shop in Hayes Valley, SF. And that is without going into the countless cases of "involuntary micro-agressions" ("oh, we don't mean you guys", "you're one of the good ones", etc.).
Outside of the bay area the landscape very quickly changes to white picket fences with two large pick up trucks and white crosses in the lawn, towns with multiple churches of different christian denominations. All of this within an hour of driving from SF. I wouldn't feel at home, and likely not be accepted as part of the community in places like this.
Because there are so many immigrants in the bay area, that gives exposure to the native-born citizenry making them less likely to treat immigrants like the feared "other", as well as immigrants treating other immigrants of different origin decently, for the most part. I think these points are what the GP was referring to. The problem of lack of systematic racism and unequal opportunities for african-americans are still a big problem in the US as a whole, and in the bay area as well, but that doesn't immediately affects the entirety of the immigrant population.