We tend to think of our state more as a Lockean guarantor of the social contract than an Aristotelian schoolmarm dispensing virtue. In other words, we assume that the state watches protectively over the citizens, interfering only when one citizen would deprive another of his or her rights. Under this view, we are independent agents who owe our virtue (or lack of virtue) mostly to ourselves.
This view of the state’s role is attractive for two reasons: First, it assumes (rightly) that the legislature will not have substantially more knowledge of virtue than the citizens. Although we should hope that those who make the laws are always “good statesmen,” the kind who know the soul and virtue, we have seen from experience that not all statesmen are good. Second, it seems supported by empirical evidence; states seem to be more descriptive than prescriptive in their moral views. We can see this in the changes in racial and sexual views in the 1960’s. There was no government mandate that challenged racism; changes won by civil rights leaders trickled up until they were codified by the legislature.
With these considerations, then, it looks like the state is an ineffective moral instructor. Bound as it is to the whims of its population, it lacks the stability to resist extremism (Nazism, for example, or whatever else is your favorite whipping boy); also, the state is no more likely to chance upon goodness just for its being a state than any of its constituents are.