It sounds like you're conflating common law with industry regulations.
If I'm a fisherman in Florida, and I need to follow regulations for the fishing industry there, they don't have a stipulation that you can't discriminate against certain persons based on age, raced, gender, etc. when you take customers out on expeditions.
Why? Because that's covered by United States law.
Yes these things happened, and yes they are atrocious but they have nothing to do with the regulatory gray areas that these companies operated in.