I could understand suing a restaurant or some places like that. The odd thing is if a photographer doesn't want to take your wedding photos, for whatever reason, why would you sue? To make him do so? What incentive does he have to do a good job?
In this day and age, the market place, IMO, is a better method of dealing with this issue than the courts. I don't mean boycotts and the like. If a business will not service -whatever- it will get around and affect their bottom line. They can then make the choice to make a different decision or have the business suffer.