Where do we draw the line between public and private behavior? Consider:

The U.S. Court of Appeals for the 9th Circuit issued an opinion last month … that people seeking roommates are shielded from fair-housing laws by the First Amendment’s protection of free association. … The Fair Housing Act prohibits denying housing to someone based on a protected characteristic, such as race or religion. It also prohibits making or publishing discriminatory advertisements for housing. …

Two years ago I undertook a study of 10,000 housing ads posted to Craigslist … 5,000 ads for rentals and 5,000 ads for roommates. … The vast majority of discriminatory ads were taken out by people seeking roommates — that is, by ordinary individuals looking for someone to help share the rent. … Most of the ads expressing a racial, religious or ethnic preference were placed by members of minority groups who were seeking roommates like themselves. …. These people were in violation of the Fair Housing Act and subject to civil prosecution.

Just as it would be abhorrent for the government to prevent people of different races, ethnicities or religions from living together, it would be equally offensive to block people of a shared race, ethnicity or religion from living together. … If the 9th Circuit had ruled differently, the potential for backlash would have been enormous and support for a crucial civil rights law would have been undermined. (more)

Surely the main reason a landlord might care about your race or ethnicity is because your neighbors might care. If your neighbors are willing to pay more to live next to people with a race they like, then your landlord might try to accommodate their preferences. So assuming you’ll have your own private room in any case, what is the difference between apartment-mate and housing discrimination? It is mainly the difference between who you’ll share a bathroom, kitchen, couch, and big TV, and who you’ll share a garage, elevator, laundry room, playground, pool, or exercise room — and of course the bathrooms, kitchens, couches, and big TVs in your lobby and community center. Is this really what we think is the difference between acceptable and unacceptable race discrimination?

I suspect the real difference is that we are willing to blame and punish landlords, who are seen as rich and dominating, but not ordinary people. If we saw Craigslist as similarly rich and dominating, we might blame and punish them as well.

What if a group took an entire floor of an apartment building, declared it all to be a single apartment, and sought the required dozens of “roommates” from a given race? If they did it without the help of a rich firm, they’d probably get away with it. But if a rich firm helped, it would be outrageous racism!

Added 7a: Imagine Romney was revealed to have once rejected an apartment because blacks lived in the neighboring apartment. And imagine Obama was revealed to have rejected a roommate in college because he was white. How different would the resulting scandals be?