You’re thinking is twisted. You make the government smaller by reducing what it does to that which the Constitutions says it may do. period.
Of course limiting government is about making the government respect its proper limits. That isn't in dispute. It's a tautology. You are arguing for the proposition that the government can, consistently with the principles of classical liberalism (John Locke and all that)destroy the sexual morality that under-girds the most successful culture in human history. Sorry but that's both crazy and utterly inconsistent with limited government. Government big enough to redesign our morality is much too big to respect any limits on its power.
Incidentally, your reference to the dietary laws couldn't be more beside the point. We didn't build a civilization on the principle that eating ham is wrong. We did build a civilization on the principle that sex is a profoundly serious matter of life and death not to be trifled with.