Here is the text of his comments.
UPDATE: The debate has started on the floor of the Senate now, on C-SPAN.
On the subject, I'll point you to one of my favorite things I've ever read on this subject-- "A really, really, really long post on gay marriage that does not, in the end, support one side or the other," by Jane Galt.
Jane is always thoughtful, and she approaches this issue from an unusual place. She's a libertarian economist with no opinion on gay marriage. In this post, she addresses the idea of gay marriage by looking at other major policy changes and the unintended consequences they had:
To which, again, the other side replies "That's ridiculous! I would never change my willingness to get married based on whether or not gay people were getting married!"
Now, economists hear this sort of argument all the time. "That's ridiculous! I would never start working fewer hours because my taxes went up!" This ignores the fact that you may not be the marginal case. The marginal case may be some consultant who just can't justify sacrificing valuable leisure for a new project when he's only making 60 cents on the dollar. The result will nonetheless be the same: less economic activity. Similarly, you--highly educated, firmly socialised, upper middle class you--may not be the marginal marriage candidate; it may be some high school dropout in Tuscaloosa. That doesn't mean that the institution of marriage won't be weakened in America just the same.
This should not be taken as an endorsement of the idea that gay marriage will weaken the current institution. I can tell a plausible story where it does; I can tell a plausible story where it doesn't. I have no idea which one is true. That is why I have no opinion on gay marriage, and am not planning to develop one. Marriage is a big institution; too big for me to feel I have a successful handle on it.
However, I am bothered by this specific argument, which I have heard over and over from the people I know who favor gay marriage laws. I mean, literally over and over; when they get into arguments, they just repeat it, again and again. "I will get married even if marriage is expanded to include gay people; I cannot imagine anyone up and deciding not to get married because gay people are getting married; therefore, the whole idea is ridiculous and bigoted."
They may well be right. Nonetheless, libertarians should know better. The limits of your imagination are not the limits of reality. Every government programme that libertarians have argued against has been defended at its inception with exactly this argument.
It's a really interesting read-- one I've remembered and referred to repeatedly since I read it more than a year ago.