Madman’s claim is that marriage equality is guaranteed by the 14th Amendment of the United States Constitution.
There's more than one way to get there, but this is one of the popular ways.
Madman further implies a claim of definition to identify how Marriage should be identified; specifically, that Marriage consists of two persons only.
I don't see where the Constitution says that. Oh, that's right, it doesn't.
Finally, he puts forth a claim of policy, writing, “We should not confuse the time when a law became unconstitutional with the point at which it “became” wrong.”We agree, and it is our position that laws denying consenting adults the freedom to marry are unjust. They are also hurtful and wasteful.
It is that particular sentence which presents the best argument for legal recognition of all nontraditional forms of marriage (same sex, polygamous and incestuous). If laws against same sex marriage were wrong before courts decided they were unconstitutional, then there is a very real possibility that laws against polygamous and incestuous marriage are equally wrong, though not yet determined to be unconstitutional.
If so, are we truly on the right side of history when advocating marriage equality for traditional and same sex couples while refusing to do the same for polygamous and incestuous couples?Good question (although I would not have worded it exactly like that.) The answer is no. The right side of history is full marriage equality. Someone may not like the idea of interracial, same-gender, polygamous, or consanguineous marriages, but their disgust or lack of understanding or religious doctrines should not prevent other people from having the marriages to which they mutually consent.