Some people get something in their heads with absolutely no basis in fact. Once that's done, it's sometimes next to impossible to change their minds. It's also usually impossible to reason with them. For example, my mother in law thinks it's perfectly ok to leave meat and other foods on the counter all day, or over night. I've tried to get the message to her, through my wife since mother in law doesn't speak English, that this is extremely risky. Even my wife isn't convinced despite me showing her info online from the FDA and various other food safety sites. I finally cured them of it by throwing away stuff I find that's been left out too long. They still don't believe me, but they know that putting things in the fridge is the only way to keep me from tossing it in the trash.

When you encounter information you can accept it, question it, which can often lead to hard feelings, or just politely listen to what they say and go research it so you can form your own conclusion. Much of what "old timers" say is based in fact, so don't blindly dismiss what they say.