I was once in a conversation with a guy who said that the basis of marriage is the production of children, hence the reason gay people ought not be married. However, he did not seem to favor disallowing sterile heterosexual couples from being able to marry. I really have never heard a rational reason why there should be any ban on any marriage. I am even in favor of allowing plural marriage. Whatever free people want to do, they ought to be able to do so long as another is not harmed.
Oh, that is just what they tell us in Sunday school to keep us off their daughters, right? How did that work out?
Marriage and the Church are intertwined about one thing only. Bastards and property inheritance. In most of the world for most all time marriage is a political play and has nothing to do with sex. The entire War Cult is arranged around dynastic wealth and the Champions of battle to sire the next generations.
Having bastards has everything to do with contested wealth passing, top dog family struggles, civil war and thus it is a Sin unto Gawwwwwwwd.
Thus is is ever so.
In Wasziiistan and the Wahabi territories, to peek at a girl and not just invite your buddy with a reach around, is a Sin unto Gawwwwwwd.
Just a different War Cult is all.