I get it as a way of making a statement that needs to be made, but I'm not a fan of countering discrimination with discrimination. Makes me wonder if something more along the lines of requiring people to make a proper|positive stand before serving them could be a better approach? In this case, for instance, "we will serve only those who will affirm that they believe that all people are valid and equal regardless of their gender identity, sexual preference, race, ethnicity, or socioeconomic status." And, before you serve them make them acknowledge and agree to the statement.