OK, after some soul searching, I have decided that I no longer oppose gays becoming married.
It's true that bigotry is the only reason to oppose gay marriage, as gays do not choose to be gay, and marriage as an institution does not confine itself to reproduction so there's no reason it should be limited to heterosexuals only.
I still will always consider homosexuality to be abnormal and unequal to heterosexuality, but abnormality should not be grounds for discrimination.
I'm still against gay adoption though, because I think every child should have both a mother and a father if at all possible.
I'm glad you've changed your views, but I would question one of the reasons you've given in support of your change of mind.
I happen to agree with you that gays do not choose to be gay. But why should the reason that someone is gay matter? If, for example, a woman somehow "chose" to be a lesbian, and then fell in love with another woman, why would you deny those two women woman the right to marry?
Consider another example: Suppose two elderly heterosexual widowers are close friends. They spend all of their time together and truly love and trust each other. They have no sexual desire for each other, but because of their age and various medical problems they have no sexual desire anymore even for women. These two men decide that they want to marry. Why on earth would anyone oppose their marriage?
This is why I believe the proper term is "same sex" marriage, not "gay marriage." And this is why I believe that any two adults should be allowed to marry.
Yes, there are people who want to use marriage to defraud the state, solely to obtain benefits (such as immigration status or health benefits). But that is the case even if marriage is restricted to a man and a woman, and there are procedures currently in place to combat such fraud. The same procedures could be applied to combat fraudulent same-sex marriages.