Your marriage does not need defending against gays anymore than white people need to be defended against blacks. I don't feel personally threatened that a black man has become president in any way. There's no destruction of my identity, no fear that I'm now an endangered species. I feel elated that we finally have someone smart who'll be running the country. It's the same with gay marriage. There's no threat to me. It's not going to change who I am, it's not going to destroy my love for some woman just because two men can say "I Do". I'd feel elated that two people have found love and wish to share it openly.
This is one issue where I disagree with the new president's stand. He does not support gay marriage, instead, he supports civil unions. They're kinda like marriage, but they're not. I do not understand how he can possibly stand for something that is essentially a rerun of "Separate But Equal". (For the record, he did oppose Prop 8.)
This is the next battle to be fought. I hope it doesn't take 40 years like the last one.