In 1960, segregation was the norm, along with the opinion hat Blacks were an inferior species. If they had held a referendum on segregation, anti-miscegenation laws and such, these would have won in he South for sure as well as a number of other places. If marriage is a basic right, then neither the state nor any referendum should be able to tell people whom they can marry.
When did marrage become a right that cannot be regulated?
I have an enumerated right protected specificily in the constitution to worship as I please , speak as I like and bear arms without impediment.
......But the state and federal authority have conspired to restrict my worship by human sacrifice , require maximum limits on Magazine and minimum calibers on my hunting equipment and I have to refrain from threatening the physical health of the president .
Why indeed must the State forbid that I marry my mother , she is an adult and I am too, after homosexual marrage I suppose I could also try marrying my son.
Why does the state have an intrest in the number of women I marry ?
And of course why is there any intrest for the state to restrict what species I wed?
It isn't hard to imagine a Polyandrus society as was often written of in the fiction of Heinlein "The Moon is a Harsh Mistress" , "Stranger in a Strange Land" etc.
Summing this up , I think it is easy to prove that the right of marrage is a right that the state can limit and until quite recently limited to one of each sex with no controversy. Removeing from the state the right to limit "marrage " to opposite sex couples really does open the door for complaints by even smaler minoritys who are discriminated against by anti beastiality , anti incest and ageist laws which serve what state intrest?
There is no real injury to correct , this is a fad that will cause its damage and blow over.