It’s been that way since the first discrimination lawsuit. It all stems from segregation days, once we decided that whole “black restaurant” “white restaurant” thing was no good it started a whole ball of wax. To me both sides are wrong, wedding photography business is tough enough without ruling out customers (especially a demographic that has more money to spend and is more likely to buy a higher priced package), and the gay couple (like everybody else) should wrap their head around the idea that some people don’t want their business and the proper response it to give somebody else the money.
But given all that it’s an old rule in contract business, going back to the early days of discrimination lawsuits, that you never say you won’t you only say you can’t. Saying you won’t opens the door to possibilities, and in that kind of lawsuit even when you win you lose (bad press, costs, lost opportunity because you’re busy in court). “Sorry booked solid then” is the correct answer.
Any business/person should be able to make up their own mind as to what customers or clients they do or don’t want. I certainly don’t want to put up with abuse from an overbearing asshat -so I don’t. My choice, nobody else’s business.