...On the morning after the election, Kristin Rothballer, 36, who lives in San Francisco, kissed her female partner goodbye on the train while commuting to work. A black woman who sat down next to her turned and said she was sorry that Proposition 8, the amendment to ban gay marriage in the state, looked like it was going to pass. “We grabbed hands,” Ms. Rothballer recalled. “And I said, ‘Well, I really want to congratulate you because we have a black president and that’s amazing.’ ” “Our conversation then almost became about the fact that we were having the conversation,”...