After they punish people for refusing to arrange flowers or bake a cake for a "gay" wedding, you don't think they will force people to perform same sex "marriage"?
And what makes you believe the coercive power of leftist judges won't go so far?
Because, legally-speaking, there is a huge difference between a private business and a religious entity. Courts (some) may be willing to force private, for-profit businesses to engage in conduct that goes against the business owner’s religious beliefs, but no court is going to force actual clergy to do so.