The problem here, as always, is that the Christian Fundamentalists have their own definitions for words.
Like in the evolution debate where they are only capable of using their definitions for words like "theory", "evidence", "fact", "transitional" etc, here we see the exact same problem.
The Fundamentalists have their definition of "marriage" - One man, One Woman and Jesus.
That's it.
They refuse to acknowledge the fact that the US Government does not recognize church weddings are sufficient for marriage.
Marriages are CONTRACTS. You sign a piece of paper, then you are married. The church, the priest, the rings, the flowers - all just for show.
Any two mentally capable adults are allowed to enter into any other kind of contract - but because the fundamentalists don't want to use everyone else's definition, then apparently "homosexual" adults are forbidden from entering into this particular kind of contract.
The solution, really, is simple:
Remove all marriage - entirely.
The state ONLY issues "Civil Union" contracts. ALL paperwork, ALL laws, ALL insurance claims, ALL medical rules, etc, ALL get changed to reflect "civil union".
Then, if you are a fundamentalist and get married by the "Church of the Bigotted Sheppard" you can claim that you are "married".
However, be aware, that ANYONE else can ALSO get "married" by ANY other figure they deem a reasonable authority.
No one is attempting to pass any laws to "force" any private religious institution into doing anything.
However, you're private religious institution likewise has no sway over anyone else's.