I don't know what your definition of a free society is but, in this society, it's been illegal to discriminate against certain, specified protected classes for a long time (it's perfectly legal to discriminate against non-protected classes, however). Those classes include religion, age, disability, race, gender and sexual preference. It's illegal for any business to discriminate against a protected class. This is really the end of the story. If you disagree that sexual preference should be a protected class, then it's your right to petition your representatives to change the law. Until the law is changed, then all businesses need to obey the law. BTW, the recent decision of a movie chain to not allow men to attend a showing of the Wonder Woman movie was illegal, for the same reason as above (gender is a protected class).