...the point and I used to agree, wholeheartedly.
The problem is that marriage, two adults joined in a union, recognizing certain rights and responsibilities, legally, is an exclusion based on the comfort level of some people. We used to argue that blacks had no rights because only people have rights and they were property, not people, therefore, no rights. Same thing with women.
In our constitution there is a guarantee of an invididuals equal rights under the law be it speech, owning weapons, being safe in your person and property, commerce, etc and so forth. None of these rights may be limited or abridged based on gender. Not voting. Not being considered a human being and not entering into a contract which is what marriage is.
We have agreed, as a people, that we abridge these rights based on age, based on behavior (criminal) and based on practical limitations such as numbers allowed such as congressional districts, members of partnerships and other contracts for practical purposes. None of these limitations have to do with what you do in a bedroom, color of your skin or what kind of gear your are packing; they apply to all.
So, I changed my mind based solely on the constitutional principle of equal rights and protection under the law. This in no way requires a given faith to perform ceremonies outside their faith, but it is to be recognized, nationwide, same as a drivers license, business contract or otherwise legal status in matters of property, rights and responsibilities.