This is truly the dumbest and ignorant argument that libertarians put forth regarding their abdication of the natural law. Marriage is the foundation of society and is responsible for the producing of productive and well-rounded citizens.
I don't approve of fag marriage, but regulating marriage isn't an enumerated power of the federal government. It's a state problem.
Then it should still be private and personal, not something the gov’t could control. Let people and the religious communities and the churches and private businesses define marriage for themselves. The people themselves can make a vast array of decisions better than the gov’t and this is no exception.