i suspect that penn and teller support ron paul because they think he is the candidate that is most libertarian. in reality, however, ron paul is not a libertarian. ron paul is a conservative, moral authoritive who borrows from the worst of libertarianism and hasn't the spine to campaign with honesty. a breif view of paul's own, sponsored legislation reveals that he is pro-life, anti-gay and ant-church/state seperation.
penn and teller both seem to be strictly against infringements of the establishment clause, and seem to despise government legislated morality. ron paul does not even believe that the establishment clause requires a seperation of church and state. ron paul's own legislation would allow local governments to interprete the establishment clause as they see fit, while barring federal courts from hearing cases regarding infringements of the establishment clause. ron paul's own legislation would bar funding for those organizations that even mention homosexuality as a healthy alternative lifestyle.
it seems very likely to me that penn and teller have simply not spent hours and hours reading about paul's past legislation. paul's own words are often very, very different from paul's legislation.
penn and teller are human. i find them entertaining, and i sometimes agree with them, but that doesn't make them immune to failure. even i fail often, and i kinda have to agree with myself...