Okay, let me try to clarify my position and how I read your position (and Jerry's and Celticlord's)
The gist of what you guys are saying is "make nice with the bad guys and they'll more readily accept your position". In other words, the anti-gay marriage folks think that marriage is for and about raising children. So focus on that and win them over. I get the logistical incentives to do that. However, it would require compromising MY values and beliefs in order to argue that. How? Let me try to explain a little better.
It requires that I go along with that presumption that "marriage is for the children". Even acknowledging that it's a valid argument for their side requires that I compromise what I actually believe.
Arguing that gay marriage is "in the government's best interest" goes against what I believe, because marriage shouldn't have anything to do with the government AT ALL, much less be "in their best interest". It's not about the government. It's about individuals and their position of equality in the eyes of the government.
See, if I just wanted to debate or make an issue about raising children, then I would simply argue that gays should be allowed to adopt regardless of marital status. But that's not what we're talking about. We're talking about marriage, which exists independent of children, is not about children, and not necessary for child rearing.
So for me to turn my argument FOR gay marriage to child rearing issues, it requires that I actually believe marriage is necessary for, or even better for child rearing. But I don't. So I can't.
Now, can I argue that homosexual couples can raise children just as well as hetero? Of course. But that has jack all to do with marriage rights.