Rusty Reno, editor of First Things, makes the conservative case against the false libertarian notion that redefining marriage will serve to "limit government" -- in fact, it will vastly expand government, he argues:

"...As marriage gets redefined we’ll see an expansion of government. That’s because gay marriage won’t just happen if government “gets out of the way.” It requires creating a new possibility that will not come to pass if traditional institutions and moral traditions are left alone. Government must intervene. Our moral traditions must be subjected to what activists think of as corrective surgery. With gay marriage we’re sure to get legislation redefining what it means to be a parent, and what it means to be a child, as is already the case in California. In the way of these redefinitions will come programs to “reeducate” John Q. Public to the “new realities.”

Here as elsewhere the progressive project is always political. It sees a problem: The pre-political institutions and traditions of society are violating rights and creating inequalities. Then it reaches for the ready tool for redress and correction, which is almost always the power of government—coercive force.

... Tyranny isn’t just a situation in which the government is telling you what to do at every moment. It’s also a society in which government says that, if necessary, it can. In this respect gay marriage reflects a dramatic enlargement of government. If legislatures and courts can redefine marriage, what can’t it intervene to reshape and re-purpose?