What is the bias/thought process that results in distrust of "formal" knowledge in favor of "folk" knowledge? An interesting effect I've noticed is that certain groups of people seem to accept "folk knowledge" and value it over significantly better founded "formal" or scientific knowledge. In particular this is notable in many discussions of Psychology and vaccinations. Scientific evidence is clearly on one side, but an odd distrust seems to exist for some which makes the unproven or disproven "folk" knowledge more acceptable to them.

This effect seems sort of like Illusory Superiority, but it seems to not quite be that; Illusory Superiority is the tendency of one person to overestimate their own abilities or knowledge. It's possible a number of biases are at work but I can't think of a single one which fully covers what's at work when one outright rejects facts based solely on other sources, rather than one's own experiences or topical knowledge (which certainly influence one's willingness to believe facts).

Is this a known/named effect? Is there anything that drives these oddly specific examples of distrust against logic-based evidence?
This might be a matter of social proof; people generally absorb folk knowledge in a less-impersonal way than formal knowledge (your grandmother says it works, instead of hearing/reading that it might work from a reporter who read the abstract of the paper that says so).  I don't know if there has been formal work examining the role of social proof in the acceptance of folk knowledge, though.