Orin, I woke up at 4 a.m. thinking about your question, and wrote the post below.
I see you've posted again. Thanks and yes you are basically getting the argument. This may make it more clear:
Orin, thanks for your question, it's a good one: why do I think a small number of gay people marrying will affect anyone else?
The most important fault line in the marriage debate is between a. people who think SSM will help a small number of gay couples and not effect anyone else and b. people like me who think this is going to change fundamentally the nature of marriage.
Obviously I think I'm in the midst of answering comprehensively (i.e. I'm not done yet guys), but let me pause to focus on your particular question, which I'm going to translate as:
"Why does what appears obviously urgent to Maggie (and many others) appear so remote and unlikely to Orin (and Eugene Volokh and a whole bunch of other smart and thoughtful people)?"
This is one of those brick walls I started out talking about, that's preventing us from "achieving disagreement."
I've thought hard about this. Let me offer two possible insights.
a. Differing implicit theory of how law affects marriage.
The now-common view (thanks largely to the SSM debate itself) is that marriage as a legal status matters because it opens the door to a host of benefits that incentivize marriage. (Thus, folks argue, the incentives for opposite-sex couples will still be the same, how can gay marriage matter? As Evan Wolfson likes to say, they aren't running out of marriage licenses.).
I don't think its true the law incentivizes marriage through benefits (although I have to confess I wouldn't mind if it were), so I also don't think this accurately describes how the law of marriage currently matters. Most people don't get anything that feels like a check from the government when you marry. Many, probably the majority of people, take a financial hit when they marry. (Through the tax code and the welfare system, see Eugene Steurele's study in the latest issue of The Future of Children).
If you think about it from a law and econ perspective, it's amazing anyone does marry. Marriage means voluntarily subjecting yourself to state regulation, paying more taxes (or forgoing the EITC), and assuming legal and financial responsibility for another person. In return for what exactly? The right to order an autopsy?
There are some big financial benefits to marriage (that are legal incidents of marriage I mean), but I don't think they are very powerful as incentives for marriage, for the simple reason that most people marry relatively young, and most of the big benefits occur after one of you is dead (a social security benefit, the right to pass your estate untaxed). Ok., there is health insurance for some people (although others upon marriage lose access to government health insurance. This latter loss may be particularly significant to young pregnant women, possibly people with HIV, too.).
So I believe, as someone whose thought pretty hard about law, public policy and marriage, that the most important remaining way the legal institution of marriage supports the social institution of marriage is in fact definitional.
Marriage's unique status at law helps draw clear public boundaries that distinguish between those who are married and who is not, allowing the more important actors who support the social institution to do their work.
Redrawing the definitional boundaries of marriage, is thus fiddling with the law's core remaining support for marriage (and we've withdrawn quite a few legal supports in recent years).
I really do think, btw, that this is what bothers most ordinary people: an instinct that their government, against their will, is telling them (and will re-educate their children) that everything they know about marriage (like the first ingredient is a husband and a wife, duh) is wrong and must now change. Upon penalty of being officially labelled bigots by their government. And everyone knows its open season on bigots in our society.
And I think ordinary folks are right about this instinct, although explaining exactly how to my fellow intellectuals may take a great deal more time and energy. (I've got two more days. . .)
b. Equality versus liberty framings.
Is SSM about liberty or equality? Due process or equal protection?
Another way of putting this is: Is gay marriage like race or like abortion?
Although there were and are efforts to understand abortion as an equality issue (for a while there you were a bigot who hated women if you were against abortion. I'm old enough to remember quite of few of these liberalish moral crusades to redefine certain people they disagree with as evil). But really what the women (and men) who support abortion actually care about is the ability to get one. So the liberty issues was predominant: Abortion advocates were willing to make certain compromises to defuse the culture wars (conscientious objections clauses for example). Today, you can be a good citizens and oppose abortion.
But race is another matter. On race the driving narrative is equality, not liberty And the result is that on race, both law and culture work very hard not to avoid but to win the culture war. Some things we won't do (like locking people up for their beliefs). But many things we will do: stripping radio broadcasting licenses from racial bigots, threatening the tax exempt status of racist organization, refusing to accredit racist schools, insisting the "respectable people" do not associate with racists (thus the GOP establishment repudiated David Duke).
I don't suspect people will try to push the SSM equality narrative to these logical conclusions right away. (And many current supporters of SSM may not want to push it this way at all). SSM architects will let the law sit there a while, work to reduce opposition, maybe wait for some generational change, before taking the next logical step.
But the main victory will have already been won, when they go to that next step: we will have decided that people who have the conjugal vision of marriage as intrinsically the union of husband and wife have no good reason for this vision and are only expressing animus.
If the principle behind SSM is institutionalized in law, and the law is able (as it is really pretty good at) to impose its values on the American people, then people like me who think marriage is the union of husband and wife importantly related to the idea that children need moms and dads will be treated in society and at law like bigots
And you are asking me why I think that might affect marriage?
I've sat in rooms where some of the most famous architects of gay marriage have made this analogy (the Christians who oppose gay marriage are just like those poor southern folks who favored segregation. We'll be re-educating them soon, and they will cave.)
The conjugal vision of marriage itself is being stamped as discriminatory and bigoted. Well, under these circumstnaces, I'm pretty sure fewer people will hold it, speak for it, try to transmit it to the kids (over the interference of government schools, who will teach the next generation that SSM was a great civil rights victory over bigots like your parents). Perhaps, under these circumstances, very few people indeed will speak up for this conjugal view.
When "liberalish" elites decide to impose their social moralities on society, generally they've been pretty successful. (The backlash elects Republicans but typically doesn't interrupt the emergence of new socially and legally enforced moral rules).
Sometimes this has been for good, as in race, in the case of SSM, I think with reckless disregard for the consequences.