I have been to this point unwilling to sign on to same-sex marriage primarily because of my understandings of the traditional definitions of marriage. But I also think you're right that attitudes evolve, including mine.
In the metaphysical elements of aesthetics the various nonmoral feelings are to be made use of; in the elements of moral metaphysics the various moral feelings of men, according to the differences in sex, age, education, and government, of races and climates, are to be employed.