(This post is by Dan Reuter, attorney-at-law here in Bloomington, Indiana. Dan got his M.Div. from Pittsburgh Seminary and served as a pastor for many years prior to entering the practice of law.)
Christian photographers, florists, caterers, etc. have been under pressure to provide their services to couples of the same sex who are having so-called "weddings." Frequently, the same-sex couples have invoked the civil rights movement, which claimed that anyone offering services to the public must provide those services to all comers, not discriminating against anyone who wants the service and will pay for it. Christians have relied mainly on their right to the free exercise of their religion, but usually they've lost and some of them have paid a heavy price—including the loss of their businesses.
They have been using the wrong strategy. There is force to the argument that a public facility must serve all of the public, and state anti-discrimination laws reinforce this rule. In our culture, "religion" is something private, that should have no effect on anyone but its practitioners. Christians dispute this, of course, but in our increasingly pagan society, theirs is a losing argument.
Here's a better strategy...
The Christian purveyor of pictures or food should tell the sodomite couple:
Of course, I will provide my stuff for your wedding. I serve, and am required to serve, everyone, whether or not I approve of what he is doing. However, you do understand that if I am at your so-called 'wedding,' I will consider it my duty to call attention to God's view of what you are doing. I will consider it my obligation to warn the guests of the danger they are running and of the harm all of you are doing to your own lives as God observes them. So, I will be distributing literature that explains all this.
And I thank you for the opportunity to reach people who otherwise might never hear this message that I believe they desperately need to hear.
There will be attempts to prohibit the Christian from making good on this promise, of course, but now the other side has the formidable obstacle of the First Amendment to the U.S. Constitution to overcome. Granted, there are limits to freedom of speech, but those limits generally relate to "clear and present danger," to shouting "fire" in a crowded theater. (Or they relate to commitments people have made voluntarily to keep national security secrets, patients' or clients' secrets, etc.)
What the other side would be seeking in this instance is to silence the expression of opinion—based entirely on its content. I doubt many courts would sanction this, and it is highly unlikely the U. S. Supreme Court would. The precedents against it are mountainous.