I respect Charles Krauthammer too much not to offer a small rejoinder to his thoughtful column today. He fairly represents my side of a debate we already had a few years' back. I stick with my position. I believe that someone's sexual orientation is a deeper issue than the number of people they want to express that orientation with. Polygamy is a choice, in other words; homosexuality isn't. The proof of this can be seen in the fact that straight people and gay people can equally choose polyandry or polygamy or polyamory, or whatever you want to call it. But no polygamist or heterosexual can choose to be gay. If you're not, you're not.
To put it another way: If polygamy and sexual orientation are interchangeable in human identity and psychology, there is no slippery slope. You're already there. Once you've allowed heterosexuals to have legal marriage, and you see no distinction between sexual orientation and polygamy, there's no logical reason to prevent polygamy. And it's straight people - and mainly straight men - who are the prime movers behind polygamy as an ideal anyway.
I think legalizing such arrangements is a bad idea for a society in general for all the usual reasons (abuse of women, the dangers of leaving a pool of unmarried straight men in the population at large, etc.). I also think it's reasonable for society to say to a heterosexual polygamist: we won't let you legally marry more than one person, but we encourage you to marry one. Now, look at it from the gay point of view. We tell the gay polyandrist: we won't let you marry more than one person, but we won't let you marry one person either. In fact, we will give you no legal outlet for your relationship, and no social support, and do all we can to stigmatize and marginalize it. Is the difference not obvious?
Gay people are not asking for the right to marry anybody. We're asking for the right to marry somebody. Right now, heterosexual polygamists have an option: marry someone. And gay people are told: you can marry no one at all. That cannot be just. It cannot be fair. And it cannot be conservative to refuse to give 9 million people an incentive to settle down and take care of one another.