I keep repeating this because I want it to sink in.
There is one argument that nullifies this marriage = religion foundation.
Atheists.
As long as there has been marriage, atheist have been legally married time and time again.
Not one law has been suggested or introduced to address atheists legal marriage.
Or to stop atheists from marriage. Or to ban atheists from marriage.
Nor has one constitutional amendment been suggested or introduced to define marriage as based only on religion.
So any argument suggesting marriage is only between a man and woman, or Christian based is entirety moot.
Marriage concerns legal matters only. And the law is often redefined or expanded to keep current with changing times.
No one person, no one group "owns" marriage. Period!
Marriage can and should be expanded with no limits as to race, gender, and if and when society has the desire to do so.... Polygamy.