In his GQ interview, Huckabee says:

I don’t think the issue’s about being against gay marriage. It’s about being for traditional marriage and articulating the reason that’s important. You have to have a basic family structure. There’s never been a civilization that has rewritten what marriage and family means and survived. So there is a sense in which, you know, it’s one thing to say if people want to live a different way, that’s their business. But when you want to redefine what family means or what marriage means, then that’s an issue that should require some serious and significant debate in the public square.

What were those civilizations that "re-wrote" marriage and died a horrible death as a result?  Was it any of those Asian societies that did away with pre-arranged marriages?  Was it the Mormons who decided marriage should be polygamous?  Was it the Jewish religion that decided that brothers should marry their brothers’ widows, and then decided they didn’t have to?  Was it the American civilization, when it decided people of different races couldn’t marry, and then decided it was okay if they did?

The truth of the matter is that every society and civilization writes and rewrites, both legally and culturally, its "definition" of marriage.  And any president worth his weight should know that.