And I am fighting the enemy in my state (Massachusetts). You make simplistic arguments against the FMA by evoking the fear of federal government taking over marriage. It wouldn't destroy federalism in marriage law.
The FMA has words; these words have meaning. If you read it and eschew the type of caricature favored by opposers of the Patriot Act, you may agree the FMA would clarify things. Like many proposed constitutional amendments these days, national and state, it is mainly aimed to reign in judiciaries.
Also, the FMA may not have to be brought to full fruition for it to have a preemptive effect. Then it again, it may.