First of all, the question is formulated in such a way as to presuppose that there *is* a rational basis for banning same-sex marriage. It would be more prudent to ask if a rational basis for governmental involvement in private social contracts exists—whether we’re talking about a ban on certain types of marriage or an approval of other types of marriage.
As a non-religious, quasi-conservative libertarian, my answer is no.
Fritz says: Marriage is a religious sacrament and goes on to say that advocating gay marriage constitutes a violation of the Establishment Clause. If marriage were indeed merely a religious ritual he might have a point…although the logical extension of that argument is that advocating straight marriage would also violate the Clause.
However the concept of "marriage" is much too complex to be classified as merely a "religious rite". The religious component is only one facet of marriage. Likewise the debate on gay marriage is an immensely complicated matter, but it doesn't really have to be. It is in fact a distraction from the more relevant question I outlined above: should marriage be the province of government at all?
First (and with apologies in advance for the length of this post) we should try to determine what marriage really is. As I see it there are three primary components of marriage: social, civil and religious.
Social: The social component is the most important. The practice itself (i.e. two people committing to a monogamous relationship) has underpinned human societies throughout history. It is important that society have a framework such as marriage because it promotes cohesion within the family unit and therefore within the community. Arguments which claim that marriage ensures procreation are incorrect: sex drive does that. An absence of marriage would not result in less children…it would only result in less happy, stable children who grow up to be happy, stable adults (who in turn rear happy, stable children etc.).
We've already seen the effects of a weak marriage ethic upon certain segments of society—look to the American inner cities. The most deplorable of these effects are upon children, who eventually grow up to procreate themselves, resulting in a downward spiral effecting everything from education to economics for generations.
Marriage as a social contract is of inestimable importance.
It is also of great importance as an emotional bond between two people who care about each other, to such an extent that for many people marriage becomes one of life's great goals. Marriage is usually considered a defining characteristic by married people.
Civil: That said, marriage is something that would exist with or without government approval. The government exists to protect its citizens from outside enemies and from domestic criminals. It exists to ensure infrastructure (roads, aviation safety, etc.). It is neither equipped to address nor justified in interfering with social contracts, whether on the micro level of granting tax credits and other benefits to married couples or on the macro level of dictating who is entitled to marry and who is not.
In short, government should be silent on the subject. It should neither ban nor advocate social contracts between individuals of any race or sexual orientation, whether marriage or for any other purpose which does not directly harm its citizens. For this reason I chafe at what Balfegor calls “the state's interest in procreation”. The “state” should have no interest in such things or in marriage at all except insomuch as it applies to the state’s obligation to protect people from harm (i.e. the children of an incestuous marriage).
Religious: The religious component of marriage is completely different from the social and the civil. It views marriage in terms of morality and religious dogma. I see the religious component as a positive thing in that it provides extra layer of commitment for married couples who happen to be religious. It strengthens marriage and therefore strengthens our society.
However this strength comes at a cost, for it is the nature of strongly religious people to see their perception of marriage (and pretty much everything else) as the only acceptable way, ordained or authorized, as it supposedly is, by God. While this approach is consistent given their worldview it can become unwieldy and oppressive when attempts are made to impose it on people whose worldview is different.
Reverting to Fritz' invocation of the Establishment Clause, the religious component rightfully becomes the sole province of religious organizations and religious-minded individuals. As such it should be completely separated from the civil component and should have no place in the debate over whether a ban on gay marriage (or any other law) should be passed. Religious dogma should not be a factor in any governmental action or consideration except in order to guarantee our basic religious freedoms.
The end result...a result based, I believe, on logic rather than on emotion or indignation...is that there should not be an amendment prohibiting gay marriage any more than there should be an amendment prohibiting or promoting straight marriage. Such pronouncements are simply not within the government’s purview.
Nor, however, should there be any penalties, legal or otherwise, imposed upon churches, organizations or individuals who refuse to conduct or honor gay marriages or against anyone who speaks out against the practice.
Marriage should not be viewed in terms of a “right”. It is not a right, it is a strong gesture and a social commitment, a promise of fidelity between two people and, if those people are religious, between the couple and God. It should not involve government in any way whatsoever. Nor should it require the approval of others (or the “forced” blessing of society, as Peter says above).
If you look at marriage from a libertarian perspective—keep government out of it and let people and religious organizations do what they want, including entering into and approving of whatever social contracts they see fit—most of the controversy over the matter would not exist.
