Michael De Dora watches Ken Burns's Prohibition and differentiates between morality and preference:
Alcohol consumption is not intrinsically a moral issue. It is an issue of preference, which is not a valid domain of law. Alcohol consumption only becomes a moral, and thus a legal, issue when it is abused and causes harm to others and/or society. When it does, we have laws to handle those situations. For instance, drunk driving is illegal and punishable. The difference between these two factors must always be kept in mind, because legislating preference is unethical and should be illegal, while legislating morality is what we ought to do.
The Dish 