Bingley's view is common sense. The new possibility of legal unions between persons of the same sex is similar to what has happened in countries with a state religion. Time was in England that the only possible way to get married was to have the banns posted (or pay for a license) and have it done in the church, which meant the parish C of E institution, by the clergy of same. No matter if you were a dissenter; a ceremony conducted elsewhere or by someone not a C of E priest or bishop didn't count in law. It took a while for Parliament to allow a marriage to take place in any other fashion.
Same in Catholic countries. You couldn't be married anywhere else but in the parish church, whether or not you were Catholic. In time, civil marriages were allowed and, in many places were actually required for civil purposes and the church ceremony was extra. It is now the practice in Italy, for instance, if you are religious, to first go to the city hall for the civil ceremony (which only takes maybe 15 minutes), then to the church for the religious rite.
In other words, old laws and legal requirements have to be modified to allow marriage to occur in such a manner that those members of the body politic who can't meet the requirements will have a chance to be married. When there are a significant number of people shut out from legal marriage by a legal bar, it is in the interest of society (and maybe the church, if your religious views are liberal) to make modifications rather than having large numbers of people "living in sin" or being forced to be at a legal disadvantage in terms of entitlements, pensions, inheritance, etc. This, I think, is what we are now grappling with and trying to do something with, the Pope, Pat Roberts, George Bush, et al. notwithstanding.
