content: No, they don't. Public accommodations have laws that they have to follow which includes not discriminating based on protected classes. In Michigan sexual orientation is not a protected class, but what a business should do (and this is what a lot did when groups tried to get bakeries to make cakes with anti-gay slogans on it) is to say "We will bake the cake and sell you the supplies to decorate it yourself, but we won't do the decorating of the messages we don't agree with." Perfectly legal.