Of course, the case for polyamory and its legal recognition presupposes that marriage is in fact what so-called "marriage equality" advocates have depicted it as being: committed sexual-romantic companionship or domestic partnership. And this is precisely what has been denied by defenders of what used to be known as "marriage" and is now called "traditional marriage" (i.e. as the union of husband and wife).
CBS reports:
A polygamous family says the landmark US Supreme Court ruling legalizing same-sex marriage shows that laws restricting consensual adult relationships are outdated, even if certain unions are unpopular.The advocates of so-called "same sex" marriage, polygamy, and polyamory are seriously confused about the central question. Why does the state recognize and bestow benefits on marriage?
Marriage, as it has been known, provides something that is of inestimable value to society. Even when it was misunderstood as polygamy this value existed. Marriage produces children, because the defining act, the most essential act of marriage is sexual intercourse between the husband and his wife.
This defining act is the means by which a future is produced for the society, which is not produced in any other way. The children, raised by their mother and father learn the value of their society and are prepared to continue that society when adults.
A society that does not value itself, its children or its future is redefining marriage to its own demise.
You should read the article by Prof. George.