For anyone who opposes SSM (and ENDA) this is really the only position you can have. Once you agree that being gay isn't a choice, there is no longer any rationale for opposition to gay rights. So opponents have to be in the choice crowd (like Santorum or Carson) or "I dont know." At least there is some consistency. Rubio tried for moderate heroism by saying being gay isn't a choice, but gays still shouldnt be allowed to get married. In my book that is worse.
It's a choice.. Plain and simple.
Eh, I tend to think it isn't. I mean, I'm heterosexual. I'm attracted to the female human, but not the male one. I don't think I could "choose" to become attracted to men, and if I could, I don't think I'd lose attraction to women. Just how I can't "choose" to like a food I dislike, or dislike a food I like.
And even if you can choose to be straight, or are a straight person thinking that gay people chose it that way, that seems rather arrogant to assume it works that way for everyone else, right? It just makes more sense to assume that gay people are telling the truth that they're gay not by choice, and give them the same rights as straight people.
Now, whether you give them extra protection from discrimination is another thing. I tend to think that "discrimination laws" of any sort are just restrictions on free speech. But I also think that restrictions on marriage, even for Biblical reasons, are also restrictions on individual liberty.