If a business clearly states whom they will serve and whom they will not then how can their be any business misunderstanding? If I go into a shop and they tell me that they do not serve red-headed women then I've wasted my time and theirs. If they clearly state that they do not serve red-headed women then I know better than to try and do business there to begin with. Isn't that a better way?
What's wrong with "We reserve the right to refuse service for any reason?" Why does the business owner have an obligation to make your search for a service provider trouble-free? He has already invested his time and property in establishing his business. He owes you nothing more at that point.