i) He who frames the question wins the debate. In the debate over SSM, Christians mustn't permit their opponents to dictate the terms of the debate. It can be a mistake to answer a question as posed, for the way in which the issue is framed may prejudge the answer. It puts the respondent on the defensive.
For instance, Christians are asked if they'd attend a homosexual marriage. But in the SSM debate, that's the wrong question. That's a theological answer to a political question.
In context, the real question at issue isn't what Christians should do, but what the state should do. What gov't should force Christians to do. Put another way, not what Christians should do, but what Christians (and citizens generally) should be free to do.
This is a public policy question, not a question of personal Christian ethics. A question of what the law ought to be. Religious rights and religious liberties are just a special case of civil rights and civil liberties in general.
ii) The First Amendment grants the right of free association and the free exercise of religion.
Proponents of SSM recast the issue in terms of what they think Christians ought to do or be made to do. They object to religious liberty on consequentialist grounds. They disapprove of Christian ethics.
But that's an exercise in misdirection. The Bill of Rights isn't based on whether everybody approves of how citizens will exercise free speech, free association, or freedom of religion. Indeed, the Bill of Rights presumes that some people will disapprove, which is why these rights must be formally recognized and protected.
The whole point of the Bill of Rights is to tell gov't to buzz off when it comes to these particular issues. Whether you think it's a good idea for Christian businesses to refuse to service SSM is irrelevant. That's not a Constitutional objection. In fact, that's an unconstitutional objection. That disregards the fact that, like it or not, Christians are Constitutionally entitled to free speech, free association, and the free exercise of religion. From a Constitutional standpoint, it's none of your business what they think, say, or do. As one student of American history has noted:
The First Amendment, ratified in 1790, guaranteed Americans the “free exercise” of religion. The Framers knew that their new republic included Quakers, Jews, Catholics, Protestants, atheists, even perhaps a few Muslims. They wanted all to be free to live – not just worship, but live – according to their beliefs.
The traditional American recipe for handling such differences is friendly accommodation. The large majority of Americans in the early republic, as today, did not believe in the pacifism of Quakers or the bishops of Episcopalians, the catechism of Catholicism or the rituals of Judaism. But they didn’t begrudge others their beliefs.
To take a comparison, we see this confusion in the way people attack gun-ownership. They support gun bans and gun confiscation because they think private possession of firearms has bad consequences. But that misses the point. Short of amending the Constitution, their consequentialist objection is a red herring.
iii) To some extent this is an American distinctive, but it has British and European analogues. Although the Bill of Rights is part of American experiment, the principle of limited government is not. That goes back to Magna Carta. Samuel Rutherford's Lex Rex is another case in point.
Likewise, in England and Europe, there was a shift from autocracy to representative government. A shift from absolute monarchy to constitutional monarchy. Then the monarchy is whittled down even further, or simply abolished outright.
In addition, during the Cold War, the free world opposed secular totalitarianism (i.e. Communism). Why go to that Herculean effort (e.g. proxy wars, counterespionage) to keep secular totalitarianism from barging through the front door if you invite it to come inside through the backdoor?