Imagine you run a commercial photography studio. The following scenario arises:
A potential client calls; it's the 'Holy Church of God is More Colourful than a Baboon's Arse' (not a real church, just in case you were wondering). This church wants some promotional shots of the congregation. You end the call saying you will provide a quote (as normal), and then quickly google the church to get a sense of their needs. My search turns up that this church is strongly homophobic. Wetboro Baptist Church level homophobic (you can swap that out with anything comparable that you find abhorrent if gay rights ain't your thing)
I wouldn’t refuse them business. What good does that do? They can just go somewhere else. I would take their money and be happy with the fact that a church is paying a baby-eating, devil-worshiping, god-hating heathen to do something. If you really didn’t want to do it, I’d quote them an outrageous price. If that doesn’t scare them off, you can take pleasure in knowing that the money you get will go to something other than religion… perhaps you could donate the “extra” money toward a cause that the church opposes.
Just a theory but, I see starting a business as entering a contract with the community. The business is there to service some need which the community has (in this case promotional photography) and the Church of "God is more colourful than a Baboon's Arse" is a part of that community....probably has been since before the business existed. On that basis, I would ignore their anti-gay heritage and take their business (charging full price of course).