The Civil Rights Act is clear about firms who serve the public.  No discrimination, especially against a protected class (which the Perry decision makes gays and lesbians).  Private bakers can, of course, select their clientele.  The only thing objectionable to any baker would be the cake topper with a rainbow flag, two brides and two grooms and if asked to do the rainbow flag in icing, I am sure a sincere baker could ask politely to beg off - but they have no right to show moral scorn to the customer.  Ever.  The baker can believe what they want but even St. Paul would say that they must be polite (a Jew to Jews, a Gentile to Gentiles).  Indeed, it is much more fun to celebrate gay people in love.  Thinking is sinful because your tribe disapproves is putting politics before people.