I want to start this by stating, I support gay marriage. This for me is a matter of personal liberty and equity. I would have preferred Civil Unions but that alternative was taken off the table. In general I would prefer the State avoid defining religious terms. There are those faiths that approve of polygamy and those unions remain civilly illegal.
The case of the baker who refused to make a pro gay marriage cake is a first amendment issue. This is not the case of a hotel or restaurant refusing to accommodate a gay couple. The cake in question is an artistic expression. There are plenty of other bakers who will gladly make that type of cake.