I hate to turn this into a Conor Friedersdorf fan club, but he recently wrote another article worth thinking about. Friedersdorf argues that because Rand Paul's positions are no more destructive or useless than mainstream policies, they shouldn't be treated as crazier. Let's concede his claim about the relative quality of Paul's policies - I don't agree with it, but it isn't groundless and it'd take a book-length essay to really make the case against it. Does it follow that these policies are (relatively) sane?
No. Sanity is determined by how widely held the assumptions involved are. Policies based on the assumption that humanity is a disease might be completely logical, but they're also insane because only psychopaths think humanity is a disease. Farm subsidies might not make much sense from an educated perspective, but the assumptions involved - that American farmers need money to maintain their production capacity and that the global food market is less trustworthy than the US agriculture industry - are very widely held. The assumptions justifying Paul's support for the gold standard - that demand for gold is more reliable than demand for greenbacks, and that the Fed is less trustworthy as a controller of money supply than the global gold mining industry is - are very uncommon and thus far less sane.
Now, it could be that Paul's assumptions turn out to be true. We've all heard the (completely bogus) stories about how Newton and Einstein were considered crazy before they won acceptance. But that's like saying tinfoil-hat wearers are sane just because, theoretically, the government really could be sending out mind control rays that only tin can defend against.