Why do you keep raising hypotheticals which have nothing to do with reality? Once again, TFA is about removing _posts_, not people.
Nevertheless, I'll indulge you: While businesses in the USA generally reserve the right to refuse to do business with whomever they please, Federal law (under the Civil Rights Act of 1964) prohibits discrimination in public businesses made on the basis of race, color, religion, or national origin. Many states also have their own laws further limiting discrimination, though I'm not personally that aware of how these have been tested in regard to online services serving many states/countries.
Beyond what's required under law, companies can have whatever policies they wish (but will have to deal with public outrage for implementing policies as disgusting as the one given in your example).
