Part of the gay marriage argument is the declaration that it is unfair to give a benefit to one group of people but not another. The usual counterargument is that such things are justified if there is some benefit to the society as a whole. How much benefit is required to privilege one group over another is variable, but the principle is usually accepted.
Leave aside for the moment the separate discussion that gays and lesbians have the same rights to get married as straights, in that they also can marry the opposite sex – in the same way that the alcohol preferer and the heroin preferer have the same rights and penalties, to legally buy alcohol but not heroin, they just value those differently. That’s an interesting take, but a bit orthogonal to my thought here. For this discussion, we will take the common framing, that straights can marry from the the category of what they want, while homosexuals can’t.
The trend in American culture has been away from confering benefits to some and not others. There were colonial jurisdictions in which only property owners, or town-born, or church members could vote. For a long time only males could, often only the white ones. We still require voters to be of a minimum age, to be citizens, and have no felony convictions. These are rules of convenience. If we had some type of accurate measurement of who amongst us is the most qualified voter, the most objective, most informed, the most thoughtful, it might theoreticallyturn out to be a 17-year old immigrant in a federal pen. Not all persons in those forbidden categories would be worse voters than all those in the allowed categories. But we have decided, with good reason, that 17 year-olds generally don’t have sufficient wisdom to privilege their opinions with the franchise; that citizens have more skin in the game; that felons have too little regard for the rights of others.
The state grants licensure to people who have jumped through certain hoops: schooling, testing, fees. Drivers, realtors, doctors, campers, hunters. Private concerns grant privileges how they wish. Usually a ski pass is acquired simply for money, but you can lose it for breaking the rules. In some circumstances, the rules will be different person to person depending on the group they are in. Age is often a factor here, encouraging young skiers or rewarding lifelong fishermen. Insurance companies know that not all smokers will die young nor marathoners live long, but they confer discounts and surcharges on the basis of the group.
Employers will note the group characteristics of HS grads or those who stayed in one job or were in the armed services. The government will let you deduct some charitable giving even though it varies widely in usefulness to society, or loan you money to go to school even though that is highly variable in benefit. For those libertarians who wish we would discontinue much licensure, I will merely argue that the principle is an accepted one in American society, and so might be accepted in this matter as well. Whether that is wise is a separate discussion.
I hope you have noticed that this creates problems for both sides of the debate. The principle is indeed allowed in many areas. We confer benefit to one group and not another all the time. Yet the key point is that we must be able to show some benefit to the society for the privilege. If insisting on one-man-one-woman marriage is indeed better for the society in some way, whether because it protects children or protects women or protects national forests, America has every right to limit marriage in that way. But it has to be demonstrable.
That many straight marriages are bad already is not a solid argument. What we need to know is whether gay marriage will make things better or worse. OTOH, a lot of traditional marriage defense is equally weak, simple declarations that we know it would be better because that fits the theory.
I give weight to the argument that we have arrived at a particular place by trial-and-error and that shouldn’t be thrown away for theory. I don’t consider it a controlling argument, else we would allow slavery and polygamy, which have also lasted a long time. But it should at least privilege the status quo while new experiments are run. Preserving the status quo is a phrase of criticism these days – usually by those who want the benefits for their group instead, for reasons no better (and sometimes worse) than the current standard.
