If it's a topic that interests you, I suggest you check out Harriet Hall's latest post at Science Based Medicine about progressive mythology in science. Lots of "natural is always better" type fallacies.
Some people in the comments are noting that libertarians and lefties can frequently wind up on the same side of some of these issues (like with water fluoridation), but I think it's slightly different for the libertarians. At least the ones that I know don't so much think water fluoridation is bad, as that the government should be letting individuals choose. That's annoying to public health people, but it's a political opinion, not a scientific one.