Similar thing when it comes to marriage ceremonies. Why lobby the state to try and force a religious institution to hold a same-sex marriage ceremony when the teachings of that religion are clearly against same-sex relationships? Can't we accept that in the diversity of opinions out there, some are like chalk and cheese? They simply don't go together so why force the issue and make everybody unhappy?
What I find interesting about this last point is that campaigners only focus on the Christian religion. It seems nobody wants to try and force mosques and synagogues to perform same-sex marriage ceremonies. Why is that?