No, I do get the point and I understand the reasoning behind it. It’s just that the full faith and credit clause doesn’t apply to a negative.
A couple getting married in Missouri is an official, legal act of the state of Missouri that other states are bound by the constitution to recognize. (Now, it could be argued that marriage shouldn’t be the business of any state, but all 50 states have chosen to get into it). Likewise for a divorce. New York used to require proof—in court—of adultery to grant a divorce. Nevada required “mental cruelty” and six weeks residency. New York had to recognize the Nevada divorce. You can argue that Nevada was negating the New York legislature’s wishes (and it was!) but that didn’t change New York’s obligation to recognize the Nevada divorce.
I believe that a major reason for the gay lobby’s effort to get a state—any state—to recognize gay marriage was the knowledge that the full faith and credit clause would push things to where they now seem to be heading.
The definition of marriage isn't a negative. It is the time-honored, natural positive definition of the legal, societal, biological relationship between a man and a woman and the children which naturally result from this union.
There is no reason we should not be able to interject this definition into other states any more than they can interject their own change of this meaning into other states.