Most of Ron Paul's worst insanity deals with issues that the President really doesn't have any power to change. His position on abortion, for example, while terrible (it's ok to ruin women's lives and control their bodies as long as the states do it!), is not something the President can do anything about. Fortunately.

Still, his views on abortion, evolution, and church-state separation are enough to make me concerned about his judgment (IIRC, he also voted for DOMA, which is appalling). That being said, his views against the drug war and foreign invasions (which the President has near-unilateral control over) would save enough lives that he would be worth putting up with over almost all other candidates. The drug war is far, far and away worse than anything Paul would do.

However, a more consistent and socially liberal libertarian would be Gary Johnson, who of course has even less of a chance. He couldn't even get on this poll.