There’s a really interesting article in the Washinton Post, Persistence of Myths Could Alter Public Policy Approach about how myths grow. As an example they used a CDC study that tried to dispel myths about the flu. After reading the flyer, many people remembered the false facts as true!
It recited various commonly held views and labeled them either "true" or "false." Among those identified as false were statements such as "The side effects are worse than the flu" and "Only older people need flu vaccine."
When University of Michigan social psychologist Norbert Schwarz had volunteers read the CDC flier, however, he found that within 30 minutes, older people misremembered 28 percent of the false statements as true. Three days later, they remembered 40 percent of the myths as factual.
So the article concludes that trying to dispel myths by stating them only makes them more memorable and more true in people’s minds!