If marriage is about creating the ideal environment to raise kids, then shouldn't gay couples who are raising children be able to avail themselves of marriage? Surely it is better for those children to have married parents than parents who are shacking up...
Short answer:
That's a red herring, and the answer is still no.
Longer answer:
I am guessing that you subscribe to the view, as Steve also does, that marriage is a civil right, and a legal recognition of commitment, that can be entered into by any two consenting adults who wish to avail themselves of that right. It's the "What harm does it do?" reasoning all over again, which I previously discussed. I am therefore also guessing that your "gays raising children" argument is a red herring, which is not so much about your view, but rather is about trying to poke holes in my view (which must be wrong, because it's not your view).
My goal is to persuade you that NEITHER ONE OF US IS WRONG, but that we are simply considering the topic from different perspectives and definitions. The point is to understand where the other is coming from. I believe that your reasoning is rock solid in defending your own perspective, and that my reasoning is rock solid in defending mine. You are arguing for A, I am arguing for B, but B is not the opposite of A. As such, your arguments for A will probably fall flat when trying to argue against B, and my arguments for B will probably fall flat if I try to use them to argue against A. It becomes a matter of which legitimate view is more persuasive to a given individual: A or B? The Supreme Court judges, being individuals, will probably choose A. However, I suspect that they are choosing between A and an imaginary anti-A, and are not choosing between A and B. I think that the entire liberal world, which supports A, thinks that they are dealing with anti-A, as opposed to B. They are partially right about that (since some people are anti-A without much concern for B), but they are also generally blind to B, which is what I've noticed.
I now come to your comment. There's a difference between looking at any individual arrangement in terms of raising children, and considering the institution of marriage as a whole, which has traditionally been our culture's ideal for producing and raising the next generation. The ideal is having a FATHER AND MOTHER. That is why marriage has existed in our society. As people fall short all over, either by having children out of wedlock, or by divorcing, the ideal is not met. I am not casting stones at the individuals involved, but I am saying that the ideal is not being met, with ramifications for the next generation as a whole. Your example of two same-gender parents raising children similarly falls short of the father/mother ideal, and does not belong to the ideal setup which is defined as marriage.
I have to ask you to go back to the premise that, because NO gay marriage can ever produce children by the coming together of its two partners, and because NO gay marriage can ever supply a mother and father, that the entire CATEGORY fails to find justification (unless you are arguing for A, as opposed to arguing against B). In contrast, man/woman marriages without children do not invalidate the existence of marriage as being between a man and a woman.
How did gay couples come to be raising children in the first place? Almost any arrangement in which gay couples are raising children points to a shortcoming somewhere: either (1) their own indecision about who they are, if they previously had children "the natural way" despite being homosexual, or (2) the adoption process, if young children were placed with a gay couple as opposed to a family with a mother and father, in the name of non-discrimination, or (3) the procreation method used, if gay couples enlisted a third party to artificially mimic the man/woman reproductive process. (Note: FWIW, I am fine with gay adoptions only when gay couples serve as adoptive parents for older children with certain backgrounds (similar to being foster parents). However, that situation does not require marriage; it's just about having a loving and supportive household. It's not enough to redefine marriage, and does not entirely fit the "creating and rearing the next generation" purpose.)
In conclusion, I think you were over-reaching with your comment. It's better just to acknoweldge that each of us has a rational reason for arguing as we do, and that it's a matter of individual preference whether we support A or B as our legitimate cause. I personally have better reasons for choosing B over A, just as you choose A over B. But, because of the incessant dialogue about A in the media (in which the B perspective is somehow rarely mentioned, to the point which people in this forum could not even surmise its existence), it has become very easy to argue for A with one-liners, whereas it takes an essay to explain B, so that A-supporters can understand (if they try).
Or maybe I'm just doing it wrong, and can use one-liners from now on to explain my position. How about this: "Marriage exists for the exclusive father/mother relationship." That would exclude all same-sex couples from fitting the definition, and it would exclude polygamy (since the topic seems to pop up sometimes when discussing gay marriage), whereas a man and woman could still be married without ever having children, because the state must not be allowed to control the choices made by the man and woman involved. People can't be compelled to have children, however the purpose of marriage is still rooted in the potential for children, and gay couples (as a category) simply don't bring that potential to the table. The childless man/woman marriage is truly the "not doing anyone any harm" relationship, whereas the same-sex relationship simply does not have the potential to fit the definition itself. That is the difference.
Of course, when I write "marriage exists for the exclusive father/mother relationship", I am essentially saying what Prop 8 was saying all along - namely, that marriage is between a man and woman, in an exclusive commitment that has its true general meaning in creating new families, in a way that steers nature into an orderly social institution. THAT is how its supporters understood that proposition - and NOT the way Jerry Brown chose to describe it, as eliminating a made-up civil right.
You might have a lot to write in response (or not), since you have always been intelligent in defense of your position. I am hoping, however, that you will recognize that you are using logic to defend A, and I am using logic to defend B (i.e. I am not attacking A), and that we have taken different positions based on how we view marriage's role in society. This is not about my imposing my will on others; it is about how I define marriage. I see no reason other than "validation" to take domestic partnernships and call them "marriage", equal to the man/woman variety. And "validation" is not enough of a reason to redefine marriage, in my view. But I can readily agree to disagree about which perspective to take.