and I've finally realized why; I'd heard the same arguments from one of my brothers:
He: It's not their ritual; they have no right to it. It can't possibly have the same meaning for them.
Me: They draw their own meaning from it. And anyway, what skin is it off your nose? It doesn't affect your use of it.
He: But it does! It distorts the whole concept, makes it meaningless!
The only difference is that my brother was referring to gay marriage.