Traditional marriage in the U.S. makes its last stand this week at oral arguments before the Supreme Court. If same-sex marriage wins out, the next question is what to do with the vanquished? Should we tolerate opposition to gay marriage?

What should be done, legally and socially, with photographers who don't want to take part in a gay wedding, or churches that don't want to consecrate a same-sex union? How should we all treat the old-fashioned view that marriage is between a man and a woman?

Many institutions, commentators and politicians already have their answer: Opposition to gay marriage deserves no more respect than racism. The government ought to force a photographer, a musician or a caterer to participate in a gay wedding, they argue, just as we forced racist diner owners to allow black customers to sit at their lunch counters.

But the premise here — that opposition to gay marriage is necessarily grounded in bigotry — is wrong.

Certainly, anti-gay bigotry exists, and if a businessman refuses to sell someone a slice of pizza because he's gay, that sure looks like bigotry. Hating or discriminating against a person purely because of his sexual orientation is not in keeping with Christ's commandments that we love everyone.

But refusing to participate in a marriage ceremony is a different sort of thing. It's not a statement about the people involved. It's a decision about the ceremony itself — that one doesn't want to endorse a definition of marriage that one doesn't share.

And there are many valid reasons to believe in marriage as being between a man and a woman. There are many arguments to make here, but here's one, from my own Catholic perspective:

There isn't really a Catholic teaching on gay marriage — there is a rich Catholic teaching on marriage, which is a sacrament. Marriage is inextricably tied with sex and family formation. To deliberately separate these three things is a moral error, the Church teaches.

Sexual morality, as taught by traditional religions, isn't terribly popular in the U.S. these days, but it's a mistake to dismiss these views as archaic prescriptions followed blindly by the faithful. Such teachings are often far more complex than simple "shalls" and "shall nots" accepted as divine revelation.

Consider Aristotle's view of virtue and happiness (eudaimonia, in Greek). Happiness — a deep, lasting happiness — is a life lived according to virtue, Aristotle writes. Morality can be seen as the roadmap to human happiness.

Over thousands of years, Christianity, building on the traditions of the Jews and ancient civilizations such as the Greeks, has tried to understand human nature ± — through experience, reason, and revelation. From that picture of the human soul, the Church has tried to craft a roadmap.

We need a roadmap because life is full of obstacles and pitfalls that we typically can't see beforehand on our own, but which are well-known in prior human experience. Walking directly towards what we think we want can often be perilous to our happiness. Sacrifice, patience, and struggle are often required.

It's not an old-fashioned or purely religious notion that sacrifice is necessary for happiness. Secular morality embraces that notion as well: You shouldn't always eat whatever you want; you need to exercise; don't get too drunk.

The road to happiness also involves giving up sex at times, even when following secular moral road maps. Perfectly irreligious, live-and-let-live moral systems often guard against (for example) prostitution, open marriages, sex in the early teen years, and extreme promiscuity. These activities may appeal to some people in the short run, but one need not believe any particular religion to understand how they can cause anguish and pain in the long run.

The roadmaps provided by conservative religious moral systems prescribe a narrower path and often call for more sacrifice. In many cases, for many people, the prescribed path is celibacy. If you want to be a Catholic priest, nun, or monk, you must also agree to a life of celibacy.

If you're unmarried, most Christian teaching tells you to be celibate. Many men and women are unmarried, despite their best efforts, and asking them to forego sex is asking a lot. But the Church does so out of an understanding of human nature, and the true path to happiness.

Married Catholic couples are often called to abstain from sex if they want to space out the births of their children. And the limitations on divorce often mean a sexless life for married people whose marriages fell apart, or whose spouses suffered a debilitating injury, or were imprisoned.

Everyone is called to some level of sacrifice — some more, some less. Nobody says it's fair. But it's prudent, the Church teaches.

For people who are exclusively attracted to people of the same sex, the Catholic Church also prescribes celibacy.

I got this roadmap image from a conversation over coffee with Eve Tushnet, the author of Gay and Catholic. Her heartfelt book makes it clear that carrying the cross of gay celibacy is very different from, and often harder than, the chastity to which other Catholics are called. But she has concluded this is her cross, and her path.

These rules, again, aren't terribly popular these days. I expect this column to persuade approximately zero people that they should give up premarital sex, birth control, or their same-sex relationship.

But however unappealing or unconvincing you find this approach to sexuality and marriage, how can you say this view is grounded in bigotry?

You don't need to agree for an instant with Catholic, or Protestant, or Muslim, or Jewish teachings on sex, family, or marriage. But if you can grant that some of these teachings are grounded, not in animus, but in an understanding of love, then at least you can agree to this: We shouldn't use the force of law to banish these views from our society.

Timothy P. Carney, The Washington Examiner's senior political columnist, can be contacted at tcarney@washingtonexaminer.com. His column appears Sunday and Wednesday on washingtonexaminer.com.