Why might a Christian refuse to attend, cater, or participate in a same-sex marriage ceremony? For simplicity's sake, let's assume this is a discussion among traditional Christians who believe—as the church has always believed and as most of the global church still believes—that same-sex behavior is sinful and that marriage is a covenantal, conjugal union of a man and a woman.
With that clarifying comment, we can address the question head-on: Why would a Christian feel conscience bound not to attend or participate in a gay wedding? It's not because of bigotry or fear or because we are unaware that Jesus spent time with sinners that leads us to this conclusion. It's because of our desire to be obedient to Christ and because of the nature of the wedding event itself.
A wedding ceremony, in the Christian tradition, is first of all a worship service. So if the union being celebrated in the service cannot be biblically sanctioned as an act of worship, we believe the service lends credence to a lie. We cannot in good conscience participate in a service of false worship. I understand that does not sound very nice, but the conclusion follows from the premise, namely, that the "marriage" being celebrated is not in fact a marriage and should not be celebrated.
Moreover, there has long been an understanding that those present at a marriage ceremony are not just casual observers, but they are witnesses who are granting their approval and support for the vows that are to be made. That's why the traditional language speaks of gathering "here in the sight of God, and in the face of this congregation." That's why one of the sample marriage services in the Presbyterian Church in America still has the minister say:
If any man can show just cause why they may not lawfully be wedded, let him now declare it, or else hereafter forever hold his peace.
Quite explicitly, the wedding is not a party for friends and family. It's not a mere ceremonial formality. It is a divine event in which those gathered celebrate and honor the "solemnization of matrimony."
Which is why—as much as I might want to build bridges with a lesbian friend or reassure a gay family member that I care for him and want to have a relationship with him—I would not attend a same-sex wedding ceremony. I cannot help with my cake, with my flowers, or with my presence to solemnize what is not holy.
In taking such a position, I've often heard things like this in response:
But Jesus hung out with sinners. He wasn't worried about being contaminated by the world. He didn't want to turn people off to God's love. He was always throwing open the floodgates of God's mercy. He would say to us, "If someone forces you to bake one cake, bake for him two."
Okay, let's think through these objections. I mean actually think for a few sentences, and not just with slogans and vague sentimentality.
Jesus hung out with sinners. True, sort of (depends on what you mean by "hung out"). But Jesus believed marriage was between a man and a woman (Matt. 19:3–9). The example of Christ in the Gospels teaches us that we should not be afraid to spend time with sinners. If a gay couple next door invites you over for dinner, don't turn them down.
He wasn't worried about being contaminated by the world. That's not the concern here. This isn't about cooties or sin germs. We have plenty of those ourselves.
He didn't want to turn people off to God's love. But Jesus did so all the time. He acted in ways that could be unintentionally, and more often deliberately, antagonistic (Matt. 7:6, 13–27; 11:20–24; 13:10–17; 19:16–30). Jesus turned people off all the time. This is no excuse for us to be unthinking and unkind. But it should put to rest the unbiblical notion that says if someone feels hurt by your words or unloved by your actions that you were ipso facto sinfully and foolishly unloving.
He was always throwing open the floodgates of God's mercy. Amen. Let's keep preaching Christ and preach as He did, calling all people to "repent and believe in the gospel" (Mark 1:15).
If someone forces to you bake one cake, bake for him two. This is, of course, a true and beautiful principle about how Christians, when reviled, must not revile in return. But it hardly can mean that we do whatever people demand no matter our rights (Acts 4:18–20; 16:35–40; 22:22–29) and no matter what is right in God's eyes.
A wedding is not a dinner invitation or a graduation open house or retirement party. Even in a completely secular environment, there is still a sense—and sometimes the wedding invitations say as much—that our presence at the event would honor the couple and their marriage. It would be difficult, if not impossible, to attend a wedding (let alone cater it or provide the culinary centerpiece) without your presence communicating celebration and support for what is taking place. And, as painful as it may be for us and for those we love, celebrating and supporting homosexual unions is not something God or His Word will allow us to do.