Misinformation should be regulated, but realistically this is the family's fault. Humans have spread "old wives' tales" since the dawn of history, ie humans will always spread misinformation, it's up to individuals to ensure that the source is trusted/proven.

Trusted/proven sources are the ones that should be protected by law; ie doctors, engineers, etc.

Otherwise let's start prosecuting everyone's grandparents for saying that throwing salt over your shoulder wards off bad luck.