Ben Gibbard wrote a short piece on his support for gay marriage, check out an excerpt below and the full text on Spin.

“When we look back on this issue, say in thirty years, it will be difficult for people to answer questions about why they were on the wrong side: “Why were you against gay marriage? Why would you feel that was the right position to take?” It's similar to someone trying to answer questions about why they were against the civil rights movement.”