I’ll give you my perspective as a young person (24) who supports gay marriage. I think there’s a fundamental disconnect between the older generation and this one, and perhaps this might help you to understand it (although I think you already do, to some extent).
Your conception of marriage, the traditional one, is that a man and a woman get married for the purpose of procreation. Marriage isn’t really about romantic love in this conception, but rather a framework for the rearing of children. If we take for granted that this is what marriage is, then I don’t think it’s bigoted at all to not have gay marriage, so long as the coupling is respected.
The problem for people my age is this: your definition of marriage was displaced prior to our lifetime. I have no memory of when that definition was true. Virtually everyone under the age of 30 has lived their entire lives under a culture that believes marriage is an expression of romantic love between two people.
So for a young person with a conservative disposition, the battle against gay marriage isn’t the same as it is for you. You’re trying to conserve something that existed in your lifetime and has since been destroyed. For a young person, there’s nothing to conserve. If the only world they know is one where marriage is an expression of romantic love, any effort to bar a group of people from that doesn’t feel like the conservation of anything, just discrimination.
I have heard this from many younger people. If, 50 years from now, marriage is basically down the tubes, except as a status symbol for the upscale, and curious historians look back and ask “why?” and “when was the turning point?”, I don’t think very many people will answer, “because in the 2010s they adopted gay marriage.” But I do think many people are likely to answer, “because starting in the 1970s they stopped believing that marriage was a social institution.”
Want an example of what “marriage as a social institution” means? In the 1960s, if you asked Americans, “Do you think a troubled marriage should stay together for the sake of the children?”, most Americans said “yes.” Today, most say “no.”
Want another? In the 1940s, while in a German prison awaiting his excecution by the Nazis, the theologian Dietrich Bonhoeffer wrote to an engaged couple on their wedding day: “From this day on, it won’t be your love that keeps your marriage alive, it will be your marriage that keeps your love alive.” In a society in which marriage is a social institution, young couples hear those words and say, “I think I understand.” In society in which marriage is not social institution, young couples hear those words and say,”I have no idea what he’s talking about.”