Just wonderin', is all

Why is a shotgun marriage of a pregnant 17-year-old and a high school boy who describes himself as a "f---in' redneck" and claims to not want kids "sacred" in the eyes of Sarah Palin and her ilk, but a marriage representing a commitment between two gay men (or women) who love each other and want to commit to each other and raise children together is somehow an abomination? Can someone please explain to me how this makes any sense whatsoever?