And the propensity for libertarians to indulge in conspiracy theories is more than guilt by association.
In contrast, government banks are "accountable" only to the whims of politicians and a public that wants its cake ("reasonable" taxes) and to eat it too (immoral entitlement programs). That's one purpose that statist banking serves: to make up for the inherent, recurring government budget shortfall by printing boatloads of money, forcibly lowering the standard of living of anyone that saves, in order to "benefit" those that won't or can't.
As far as conspiracy theories go, it depends on who you're talking about. It also depends on the conspiracy theory. Conspiracies do exist; the phrase "conspiracy theory" has of late been used as an effective tool to dismiss what used to be called investigative journalism or social criticism. Anyone advancing a criticism of the social order or putting forward the outrageous idea that powerful people might organize to maintain their power is a "conspiracy theorist." Obviously powerful people are rational, egoless, dispassionate technocrats and are only concerned with the public interest. All praise the great steersmen!