I was watching Glen Beck today, who suggested that legislation supporting marriage equality has a more sinister motive of suppressing church religious freedoms. This argument, or some variation of it, has appeared in a number of anti-same-sex-marriage public campaigns. For a great example, take a look at the (fantastically well-designed) Yes On Prop 8 ad archives.
The idea is this: churches should be able to decide whether or not to perform marriages in accordance with their religious beliefs. Legislating that all church perform marriages for same-sex couples who approach them would be undue government interference in religious self-determination.
On the other hand, if legislation defines marriage as between one man and one woman, then a significant number of churches (for example Reform Judaism, the MCC, UCC, and various progressive congregations) are essentially prohibited from exercising their own religious beliefs.
"Ah, but that's quite different," You might say. "We shouldn't set up the laws to allow churches to do whatever they want. What if a denomination refuses to acknowledge interracial couples in marriage?"
So perhaps churches should be restricted for larger social concerns. Of course, that brings us right back to the possibility of legal same-sex marriage. And in all likelihood, more churches will be affected by not being able to perform desired marriages than would be forced to perform undesired ones. Canada's had same-sex marriage for roughly five years now, and their legal structure doesn't require pastors to perform marriages if they don't agree. In fact, the same goes for the Netherlands, South Africa, and Norway. So why not advocate—if religious freedom is really your concern—for marriage equality with clauses ensuring churches won't be forced to act inconsistently with their beliefs.