Socialism to most Americans is free healthcare and college. Capitalism is lobbying and the abuse of government sponsored monopolies.
That said, yes, the feudal lord's band of merry thugs would keep the peace, because peasants can work harder if they're not squabbling with each other.
You don't have to go that far back in time:
The gray area, which I consider to fall in the 'upholding the rule of law' category, are consumption-based regulations or incentives, where a practical piece of society (like burning fuel) infringes on the rights of many others to a small degree, and this is where a carbon tax could easily fit in a free market system. In fact, it could be argued that the system is freer than if there were no pollution taxes at all, because then people would be allowed to infringe on the property rights of others (via shared atmosphere, oceans, climate) unhindered.