When I saw this post, I simply don't get what the premise of this ruling is.
Assuming that this is a case solely about commerce (it isn't really since there is an issue of art in commerce). Why can't the photographer simply refuse to take that business and not offer any grounds for it?
I have to assume that the photographer said that she won't photograph a same-sex commitment ceremony and that reason led to the complaint to the state. If that is not correct, then this post is going to be off a bit.
the first question is why not simply decline to take the business. Cite no reason or if pushed say that the time is previously booked. Why cite the same-sex issue?
Second, when did photography become a "public accomodation?" Hotels, restaurants, etc. are accomodations, but not photography.
Third and finally, when did it become the norm for the state to say that a businessman or businesswoman is incapable of determining who will be their clients and who will not. Business owners routinely turn down business for all sorts of reasons. Who is the state to say that a business can or cannot refuse service to someone.
Lots of good stuff at Volokh Conspiracy on this one.