I believe marriage is inherently between a man and a woman by definition. Therefore it's incoherent to speak of same-sex marriage; that's not what marriage is. Most people posting on this topic seem to think that marriage is just a social convention adopted by society - like driving on the right, or left-hand side of the road. We could just as easily adopt the opposite side of the road as convention. Or even reverse the function of the colours of our traffic lights (go on red, stop on green).
In the words of someone much more intelligent than myself, 'I would say that marriage has always and everywhere been defined and understood to be between a man and a woman, and that, therefore, the union of two persons of the same sex, whatever you might want to call it, just isn’t marriage. It would be as if someone wanted to redefine what it means to be an heir of someone else. Suppose I say, “I want to be the heir of Bill Gates,” and someone says, “Well, you can’t be. To be an heir you have to be designated in the will. You have to be a legal designee,” and I say, “Well, no. I don’t think we should define heir that way. I think an heir can be anybody who would like to have that fortune, and so, that is the way I think an heir should be defined and therefore, I want to be an heir of Bill Gates, and I am his heir.” Well, I think you can see that is just absurd. You are just arbitrarily redefining words. That is not what they mean. Similarly, I would say the same thing for marriage."
Furthermore, the title of this thread is Gay Marriage, whereas it should really be Same-Sex Marriage since it's differentiated from 'regular' marriage through gender, and not through sexual orientation. Gay people have been perfectly free to marry - just not to members of the same gender! So opposing same-sex marriage on these grounds isn't a question of discriminating against homosexuality.
People seem to be convinced that to oppose same-sex marriage is to be intolerant, to be close minded, and to be bigoted against a certain class of people, but I disagree. Tolerance should mean, “though I disagree with what you say, I will defend to the death, your right to say it.” So we tolerate people but we discriminate between views. We discriminate views as true or false though we tolerate those who advocate false views. We recognize their right to an opinion and their right to express it. But in the new tolerance, the kind of new value that has been accepted, you discriminate against people but you tolerate all views. So, that you tolerate same-sex marriage as well as traditional marriage. You tolerate all the views, but now you will discriminate, for example, against those who hold traditional views, by calling them bigots and intolerant and rejecting them and vilifying them.
And I expect my views to be tolerated