They should hire in a judge for weddings they don't want to participate in.They are ordained pastors of their church, so of course they are acting on behalf of their church. This is the reason why the state recognized their authority to perform weddings in the first place.
I still think that if they want to run the type of establishment that picks and chooses their clientele there are ways to do that. If they want doors open to the public then they're gonna have to figure something out.
But of course, this was the sum of all fears going in, so no one is looking to make this easy. It's all 'bout scoring them points.