Very good point. A contract first needs to agreeing parties... initially, either party can refuse for any reason to enter into the contract. Once the contract is entered into, the terms initially set forth are biding. That is contract law, in a nutshell. There was NO contract in this case... had the photographers initially agreed, and then failed to provide the service, then they should have a case.
But the court isn't acting based on a contract complaint, they're acting based on some touchy feely "civil rights" complaint and that changes everything drastically. Welcome to 1984.