That's a question I've often heard from opponents of same-sex marriage. They can't understand why civil unions aren't good enough, why gay and lesbian couples have to lay claim to the term "marriage" - a term they seem to consider theirs and theirs alone.
They often base their argument on the contention that same-sex marriage is outside the bounds of their religious tradition. It's sinful, evil and to their way of thinking, a threat to their way of life. Of course, it isn't threat - this is pure rubbish. No one in favor of same-sex marriage wants to criminalize marriages between men and women. What they want is equal access, pure and simple.
Gay and lesbian couples are the ones being denied the opportunity to engage in an activity that's open to others. Yet those who would deny them this opportunity claim they're the victims. They say same-sex couples are denying them the right to practice their religion. Yet the only way this could possibly be true is if their religion somehow demanded that everyone on planet Earth conform with its code. Not just believers. Everyone.
Labels are important in this process, because people find their identity in labels. You can say it's just a piece of paper, but a marriage license symbolizes something far deeper to a couple. The same holds true for other labels that are viewed as expressions of identity. At various points in history, the church establishment refused to recognize groups such as the Gnostics, Cathars and Lutherans as Christians. Instead, they were heretics. The name "Christian" could only be claimed by those who swore allegiance to Rome, with the Catholic Church holding a de facto trademark on the label that was enforced at the point of a sword.
Why was this important? Because those identified as heretics posed the same sort of threat to the establishment as same-sex marriages pose to straight couples: the threat of an alternative. The possibility that their way wasn't the only way. And this scared the bejeezus out of them. Galileo was silenced for the same reason, even though he could offer scientific evidence to back up his claims (made earlier by Copernicus) that Earth wasn't at the center of the solar system.
When you get into the realm of religion, evidence can be scanty. Instead, most assertion is generally based upon authority and tradition. There's nothing wrong with this in and of itself. Many traditions took hold because they made sense at a certain point in history and subsequently "stood the test of time." The problem arises when traditions stop being subjected to this test - when they are defended, not because they are effective, but rather for their own sake.
The geocentric model of the solar system probably made sense to a lot of people for a lot of years. It stood up to certain observable tests: the stars appeared to rotate around Earth, as did other heavenly bodies such as the moon and sun. To the casual observer with limited resources to test the idea, it must have made pretty good sense. The problem occurred when people insisted on holding to the tradition in spite of clear evidence that it was false.
This is like saying, "It works because we've always done it this way," rather than, "We've always done it this way because it works." Following tradition for the sake of tradition is getting it backwards, and since humanity tends to gather new information as time progresses, the idea of viewing the world through an ancient lens doesn't always work.
It would seem a simple enough matter to adapt to new information by modifying one's worldview. New information in the 16th century indicated that the sun was at the center of the solar system. Relatively new (within the last half-century or so) information in our own time suggests that homosexuality is not a choice, as previously assumed, but an integral part of a person's identity.
But too often, religious traditionalists refuse to acknowledge such new information because they view the old information as authoritative. It was written down in a sacred book, incorporated into time-honored dogmatic teachings and passed along by figures who claim authority - priests, seminary graduates, pastors, high priestesses, imams and so forth. Such figures seek to preserve tradition for tradition's sake precisely because they have a stake in the game. Their authority is being challenged, and to admit they might have been wrong would shatter their reputation as the ultimate arbiters of truth.
Sometimes, we become so caught up in the new information that we too quickly rush ahead, abandoning "old ways" that may have worked better. This is not because we tested the old ways too rigorously, but because we failed to test the new ways rigorously enough, throwing ourselves headlong into new technologies before we've sufficiently worked through the implications. Sometimes, it's best to return to older ways of doing things - sometimes, but not always, and not simply for tradition's sake.
A line from Tim Minchin's song White Wine in the Sun comes to mind here: "I don't believe just 'cause ideas are tenacious it means that they're worthy." The word "just" is important here. Some tenacious ideas are worthy; others aren't. They're worthy if they work; they're not if their tenacity is the result of authoritarian attempts to take and/or consolidate power. The motive behind continuing a tradition will tell you a lot about whether it's worth continuing.
All of which brings me back to the topic of labels. There are those who seek to hoard labels to themselves - whether they be husband, wife, Muslim, Christian, Pagan - based on tradition alone. They defer to the god(s) they worship as authorities for excluding other possible viewpoints and disparaging new traditions in order to reclaim or preserve what's always been comfortable. Where compelling evidence is lacking (and even, as in the case of Galileo, where it's present), they seek to have their beliefs accepted as a substitute. Then they seek to force their viewpoints on those who don't agree as a means of validating their dubious or even erroneous conclusions.
True marriage is reserved for one man and one woman. True Christians don't (or do) speak in tongues. Real Pagans worship the gods. Real Wiccans are Gardnerian. True Muslims are Sunnis (or Shiites). Real men eat steak.
Who says? The self-appointed authorities who believe they're speaking on behalf of a divine agent. The problem lies in the fact that the divine agent him/herself never seems to speak directly and incontrovertibly to humanity - or even a significant segment of it - simultaneously. We're asked to believe that the self-appointed authorities are the "true" authorities, that their decrees outweigh any evidence to the contrary and that their interpretation of scriptures and doctrines is the correct one.
The tenuous nature of such a belief is exposed when two authorities conflict (the mutual excommunication by the patriarchs of Rome and Constantinople in 1054 is a great example) or when evidence and public consensus overwhelms some previously accepted tradition. I have to laugh when I think about the two patriarchs telling each other, "You're not a Christian, goddammit! To hell with you!"
The common thread in all this is that such condemnations are always focused outward - not toward the self, but toward the perceived "other." Rather than focusing on controlling themselves, such self-appointed authorities spend most of their energy trying to control others. Those on the receiving end of this process usually have no interest in controlling anyone; they simply want to live their own lives while enjoying the same rights and privileges their accusers enjoy ... but seek to deny them. The right to marry whom they wish, regardless of sex. The right to call themselves Christian or Pagan or Muslim. The right to believe as they please without being told that their belief is an "offense" to someone else.
That shouldn't be a burden on anyone, and it shouldn't be too much to ask.