a quick Google search would yield enough facts to disabuse them of their notions

Most people are not strategic enough to use google. Or if they get many contradicting results from google search, they are not smart enough to decide.

Also, there is this bias that if an information was brought to you by a person you know, it has much stronger impact. (For most people, good relationships matter more than truth. If someone brings you an information, disbelieving the information is a potential conflict with given person.) You only get an equal opposing force if another person you know opposes the original information. For example, by saying "it's bullshit" and posting a link to refutation.