Wrong. We have to agree on a system and then it has to go all ways. All ways.
If we want total, free market systems, anyone can refuse anyone for any reason. SHS can be refused, the gay couple can be refused, a black person can be refused, a white person can be refused. Anyone can be refused cause someone doesn't like the jeans you're wearing. Total free market; no restrictions.
We can go where almost no requests are refused. You own a bakery, you will bake a cake for anyone who walks in the door. You're Jewish, you will bake a cake for the Nazi rally. You're Muslim, you will bake a cake for the gay wedding too. Etc, etc, etc. If you agree on this system, a business owner is almost an indentured servant of the customer.
I take a middle position, where generally the free market should be allowed to operate with some boundaries. I do not believe people should be refused based on "who they are" but I believe some events should be able to be refused especially when there are deep religious objections or the request is obscene, etc. The Red Hen did not fall under this because SHS was simply eating a meal, as all humans do. It would be akin to a Christian restaurant owner refusing to serve a gay couple a simple meal. Which to my knowledge has not happened.