And that document bears out the point made by EdT, that marriage is a universally recognised arrangement, .
And if you change it, it won't be.

Marriage has been exclusively for MF for millennia.
(Let those who deny that produce examples please)

In my lifetime, SS marriage was simply unthinkable.
I have come to accept it, but you can not expect everyone in the world to change their perspective on the same day!

It would be unthinkable to refuse female suffrage now, but it's acceptance was within living memory.