Some straight people have gradually changed their attitudes toward gays after realizing that their friends — or children — were gay. Researchers have found that male judges are more sympathetic to women’s rights when they have daughters. Yet because of the de facto segregation of America, whites are unlikely to have many black friends: A study from the Public Religion Research Institute suggests that in a network of 100 friends, a white person, on average, has one black friend.

That’s unfortunate, because friends open our eyes. I was shaken after a well-known black woman told me about looking out her front window and seeing that police officers had her teenage son down on the ground after he had stepped out of their upscale house because they thought he was a prowler. “Thank God he didn’t run,” she said.

One black friend tells me that he freaked out when his white fiancée purchased an item in a store and promptly threw the receipt away. “What are you doing?” he protested to her. He is a highly successful and well-educated professional but would never dream of tossing a receipt for fear of being accused of shoplifting.