Homogeneous groups are not surprising or wrong, what I object to is the hypocrisy of so many progressives on race.
Aaron M. Renn at the indispensable New Geography site has a fascinating analysis of a curious aspect shared by progressive urban havens like Austin, Portland and suchlike: they have relatively few black people in them. Excerpt:
This raises troubling questions about these cities. Why is it that progressivism in smaller metros is so often associated with low numbers of African Americans? Can you have a progressive city properly so-called with only a disproportionate handful of African Americans in it? In addition, why has no one called these cities on it?
As the college educated flock to these progressive El Dorados, many factors are cited as reasons: transit systems, density, bike lanes, walkable communities, robust art and cultural scenes. But another way to look at it is simply as White Flight writ large. Why move to the suburbs of your stodgy Midwest city to escape African Americans and get criticized for it when you can move to Portland and actually be praised as progressive, urban and hip? Many of the policies of Portland are not that dissimilar from those of upscale suburbs in their effects. Urban growth boundaries and other mechanisms raise land prices and render housing less affordable exactly the same as large lot zoning and building codes that mandate brick and other expensive materials do. They both contribute to reducing housing affordability for historically disadvantaged communities. Just like the most exclusive suburbs.