Well, the SCOTUS just decided that same sex unions are, in fact, weddings and sex is an existing protected class based on actual legislation and precedent. That means the baker would be discriminating illegally as a public accommodation on a federal level if they refused their service based on the sex of that event's participants.

Public accommodations are not prohibited from discriminating on the basis of sex by federal law.

Furthermore, the bakery is probably not a public accommodation under federal law unless it's principally selling food for consumption on the premises.

And, by same reasoning, the consequences to clergy are ...?

Non-existent because they do not provide a public accommodation and are exempt from legal entanglements based on discrimination.

IOW, even though they provide a service, it is not the same class of service, legally, as a cake maker or any other for profit entity serving the public.