So it appears that everyone so far has a "live and let live" outlook on this. Which is in my opinion is great regardless where it comes from and so far no one has really thrown a moral judgement on said individuals. I would like to step back the position of not concerned with laws. Though the letter of the law as it is may not be important it can certainly be relevant to what we think a position should be.
So my outlook is a bit of a mix. I'll start with this "Everyone want's to be a gangsta til its time to do gangsta shit". I adapt this in my own life and social circles (I live in CA and work in San Francisco so that gives you an idea) to illustrate a point. "Everyone wants to be a liberal until it's time to do liberal shit". Which I have to remind leftists on how illiberal they are when they claim otherwise (note: I don't think the two are the same). Defending rights is easy when its for people you like and agree with. The real test is doing it for the opposite. In my view, the most important group to defend is the unpopular one. "every time you violate or propose to violate the free speech of someone else, in potencia, you’re making a rod for own back." - Christopher Hitchens. Because if only comfortable or popular views/speech is allowed whats the point of the first amendment? How long before you become the minority voice and are subject to the same treatment?
The protection of religious rights should be done from the perspective of protecting the rights of the individual first rather than the group. In addition to this you also have to take into account the basic societal laws and customs.
Lets take an extreme example for clarity. In the case of honor killings for Islam: The group in the U.S. may decide within their religion that killing a girl is acceptable. But if we apply the previous perspective that A the individual has their own rights, and B: the custom of the land is that murder is bad we come to the conclusion: that even under religious reasoning their right to practice religion doesn't supersede the girls individual rights.
Now applying it to the main example: a religious business owner (Because every single Abrahamic religion has text that prohibits homosexuality not just Christians) that decides they do not want to contribute to a gay wedding. The gay couple in this case, is soliciting the business owner for a service. In this case the business owner is not preempting a religious act that effects the couple in any way, it is the couple that is asking that the owner conduct an act. Because of this the owner can site religious grounds to refuse said service because it doesn't infringe on the couples rights nor does it violate any local laws (most of the time) and customs. This would immediately change if the owner was for example an ER surgeon and was refusing to give life saving medical care. Simply because the custom (and likely the law) dictates that if you are in said position you can't refuse.
Now does this apply to all services? Lets say a customer is just looking for a cake and just happens to be gay? Could he refuse in this case? Currently under the law no because of anti-discrimination laws. But isn't this logically inconsistent? Is that ok? and if yes where's the line? On that one I would need to think it over a little more.