Not dumb at all when you consider the original intent of the Constitution was a limitation on the federal government only. In effect what you are doing by passing such an Amendment is limiting the states to handle their internal affairs as they see fit. Some states will pass DOMAs, some will not. However passage of an Amendment requires the states to adhere to the federal standard, thereby limiting the rights of the separate and sovereign states.
Of course even the most inept conservative would understand this by reading the Federalist Papers and the promises made by those three authors. But who said social 'conservatives' and Republicans were conservative at all? They just want their way.
Sorry, but 3/4s of the states have to assent to an amendment. So it is a willful agreement between the states and the fedgov, unlike most regular federal legislation which I doubt the author has a problem with.