I have intended to keep up my end of the same-sex marriage conversation with Matt of Unlikely Words, but various factors have delayed my doing so. For one thing, life keeps trying to trip me up (in ways stated and hinted on Dust in the Light and in ways kept private). Perhaps a more significant, specific reason is that, having argued this subject for so long and from so many angles, it’s difficult to muster motivation to repeat arguments that are readily available should one search Anchor Rising or Dust in the Light (or the Internet, for that matter) with a few well-chosen keywords. Rhetorical constructions of the type “I have yet to see an argument” evoke in me an especial weariness; anybody who’s looked ought to be better able to restate the actual opinions of those who oppose SSM. Lastly, if I’m to make due admission of pride, I find unnecessary usage of the editorial “sic” — as if to imply that I do not write as carefully as I ought — discouraging. But Matt has offered his position eloquently and with clear intention of fair discourse, so I’ll try to do the same, and I do apologize for taking so long.
The place to start is the heart of the matter. Matt is flatly contradicting himself when he writes that “any religious person should be free to decline to… acknowledge any marriage that offends his or her beliefs.” Earlier, when differentiating between discrimination against gays, in not being considered eligible to marry each other, and that against Christians, in not being able to conduct their business or charity in keeping with their belief that marriage is fundamentally a male-female relationship, he wrote:

I’ll grant that, in a world where same-sex marriage is legal and discrimination based on sexual orientation is illegal, the invitation company might not be free to refuse to print invitations to same-sex marriages. Let’s also grant that, if they take public funds, the Christian agency might not be free to decline to place children into households where both parents are of the same sex. Their definitions of marriage would suddenly come into conflict with that of the state and, indeed, they would be guilty of legal [sic] discrimination.

It may not make a significant difference, but it’s worth noting that the Christian adoption agency faces a more essential repercussion than simply the loss of public funds; at least in Massachusetts (from which state my example derives), organizations offering such services must register with the state, and the Catholic adoption service found that it could no longer perform its function at all. Matt may take the position that the loss of a license is merely the reasonable consequence for refusing acknowledgment of same-sex marriage — which the agency is still free to do, in the abstract — but I imagine that I’m not alone in thinking that the coercive power of threatening a vocation (in both professional and religious senses) is tantamount to a denial of freedom. At the very least, that argument takes the same form as an opposing one, that homosexuals are merely not able to register their “marriages” — into which they are still free to enter on a private basis — with the state.
If Matt’s “rubric to decide which [instance of discrimination] is worse” entails “evaluating the harm done to the class or individual discriminated against,” I wonder what scale places public recognition of a relationship above the ability to enter into a field of work. Would it be worse to deny homosexuals a right to redefined marriage or to bar them from becoming (say) teachers. Matt may argue that the Christians are still free to provide adoption services, just under a rule that conflicts with their beliefs, but again, that statement takes an identical form to my argument that homosexuals are not barred from marriage — they just prefer to form relationships with those to whom they are sexually attracted (a preference that is certainly understandable).
Why is it a violation of “a simple question of civil rights” to state that marriage’s meaning, at least inasmuch the government is justified in dabbling in it, involves something other (and more) than committed sexual intimacy, thereby excluding homosexual relationships by its nature, yet it is not a violation of the Bill of Rights to insist that Christians must be barred from placing children with adoptive parents in accord with their beliefs? In what way is more harm done by disallowing gays from redefining an age-old institution than by disallowing Christians from shaping their society in accord with their beliefs?
People can reasonably accept or refute these various arguments, whether they are of the same or different form, but if we are to work together to determine the best directions in which to develop our society — rather than manipulating the law and plying politics to force our own views to the fore — then we must seek at least the empathy that comes with understanding how the other side has arrived at its conclusions. And if we are to construct our own arguments in a way that is comprehensible to those who begin from different worldviews, then our examples and analogies must compare like to like. On topics related to homosexuality, comparisons with racial discrimination seem usually to shirk this imperative. Writes Matt:

… I don’t consider the imposition of equality to be discrimination. Was the decision in Brown v. Board of Education discrimination against segregationists? Surely not. Of course, the two cases are not entirely parallel. The distinguishing factor seems to be that the objections are motivated by religion rather than some other value system.

Actually, the cases are not entirely parallel because, in Brown, the court was imposing equality, while SSM imposes a definition of “marriage.” The parallel would be if, in the name of racial equality, the Supreme Court had redefined “school” in a way that would increase the ease with which underprivileged blacks could acquire diplomas. Similarly, and more germanely, comparisons of SSM with miscegenation elide the fact that people of all races could enter into marriage, as it was understood by all, with the dispute being over whether a male of one race ought to be able to marry a female of another. The point is that the traditionalists in my examples are not discriminating against gays qua gays, but in favor of marriage under their definition, and since marriage is a cultural institution with implications for the society’s health, such discrimination is legitimate.
It’s worth noting, here, that the discriminatory definition of marriage is not “the traditional religious view,” as Matt would have it, but the traditional religious, historical, cultural, and legal view. Moreover, it is not the case that traditionalists are trying “to make it the law” (therefore necessitating “extra-Biblical justification”). It is already the law, and legalistic obfuscation aside, everybody knows that it has always been the law. The burden is on those supporting a redefinition to explain why, now, all of a sudden, we must treat the legal meaning of the word “marriage” differently.
Back in 2004, Andrew Sullivan attempted to address this problem by arguing that coupling is now “the de facto meaning” of marriage for a majority of people who are married. As I pointed out at the time, that’s simply not true. It is safe to say that almost all married men and women already or will have children. Matt offers a few “marginal cases” to prove that “defining marriage as a procreative pair cannot be sustained”:

Can a heterosexual couple who are (independently or mutually) infertile be said to be truly married under this definition? What about a married couple that abstains from sex? And do we want the state to invalidate marriages that do not produce progeny, or require fertility and genetic testing before validating a marriage certificate? Do we want the state to compel married couples to attempt to conceive?

Addressing infertility (with reference to an older post):

• Infertility is most commonly seen as a problem within marriage precisely because it makes it more difficult to fulfill a central role of marriage. It therefore cannot be said — as I said of SSM in the quotation to which Matt is responding — that it will “erode the institution’s utility.” If anything, it affirms the procreative emphasis of marriage.
• It needn’t invalidate a marriage, because infertility is not sterility, and most infertile couples do not ultimately prove to be sterile. (I know I did the research on that, once, but I can’t find my resulting writing at this time.)
• Couples will not generally know that they are infertile, much less be able to give therapies a chance, until they are attempting to have children, and it is precisely the attempt to have children that our society wishes to encourage taking place within the context of marriage.

That last point leads to a more fundamental one, of which it is easy to lose sight in a debate that has as its focus achieving marriage rights for homosexuals: Marriage isn’t positioned in our society as a form of reward. (That credit card commercial in which the king declares the dragonslayer eligible to marry his daughter comes to mind as contrast.) Rather, marriage represents an arrangement into which we wish to usher those pairings that are likely to create children. Therefore, raising barriers such as fertility testing and affidavits of procreative intent would generate disincentive.
I’ll rephrase for emphasis: The essential idea behind public encouragement of marriage is to draw people whose behavior makes conception likely within its structure. This is what we who oppose same-sex marriage are trying to preserve. We do not, as Matt apparently misconstrues, see marriage as a route toward procreation; indeed, pushing people into lifelong monogamous relationships would seem likely to decrease the rate of childbirth. Incorporating homosexuals into marriage would erode the notion that marriage and potentially procreative relationships ought, in principle, to be synonymous in a way that including sterile and abstinent couples does not for the prima facie reason that the former requires said notion’s explicit rejection. If one does not accept the proposition that even abstinent couples — in their conspicuous incongruity — affirm this link, then at least it can be said that the opposite-sex aspect of marriage’s definition, which abstinent couples do not threaten, is sufficiently specific for society’s purposes. (And besides, abstinence is not an inherently permanent state; some might even call it tenuous.)
Indeed, it is advocacy for same-sex marriage that leads Matt to wonder, “Where, in any of this, should gender matter?” — “this” being “the strengthening of familial and societal ties, the establishment of persistent kin groups and affinities, and the financial stability of combining households, benefits, and assets,” which he acknowledges as social benefits of marriage. Well, absent the expansion of those familial ties into future generations via procreation, where in any of that should number matter? Or preexisting relationships, such as exists between siblings?
To accept those subsequent claims to the “civil right” of marriage would be to make marriage essentially meaningless. To reject them would require a form of discrimination substantively no different from that of which traditionalists are accused when it comes to homosexual marriage. Actually, I take that back; it would be different — more capricious, more invidious. Matt’s correct that “not all discrimination is equal.” Some discrimination is advisable, as between good and bad clams, as between productive and wasteful activities, as between classics and popular fiction, and as between relationships that tend toward childbirth and those that inherently do not.