Excellent insight! It's to bad that uncommon common sense is needed to appreciate that insight.
I think there's more to it than that. If they want to call themselves married, that's their business. But what they're saying is that WE have some obligation to recognize it. No one can have a 'right' if that 'right' puts an obligation on anyone else. You have a right to free speech, but that doesn't mean I am obligated to listen to you. You and you brother/sister can call yourselves 'married', but we as a society are not under any obligation to recognize it.