Getting back to the topic of the thread - if other "public accommodations" are going to be forced to service gay weddings, churches should follow the same laws as the rest of us.
Churches do follow the same laws as the lowest common denominators.
What evidence do you have that such is not the case?
If bakers, and other service providers are to be legally required to serve gays, there's no reason churches should be excluded.
Bakers are not protected by a Constitutional amendment. We could argue whether or not individuals engaged in baking cakes should be allowed to opt out based on the first amendment, but churches are very clearly protected.
How so? Are public accommodations laws "regarding the establishment of religion or prohibiting the free exercise thereof"? Because that's all the First Amendment has to say about religious protection. Ironically, public accommodations laws to violate the First Amendment, but not in the way that you seem to think. They violate it by offering special protections for religions - which is pretty clearly "law regarding the establishment of religion".
The intent of the religious rights guaranteed by the Constitution is to keep government out of telling people which religions they can and can't practice, not to give members of officially recognized religions special privileges.