Separation of church and state do not allow you to sit in judgement about the right or wrong of someone's religion.  Religious rights are protected by the Constitution.  No one is preventing or forcing gay couples not to marry, as the courts should not allow gay couples to force religious persons to participate in any wedding that they are uncomfortable with.  They can buy muffins and cookies, but there's no reason they can't find plenty of people supportive of gay marriages, to bake them a cake.