Why are we so ignorant about biology that quacks gain popularity?

[Marvin]

I say, let those shitheads stop taking vaccines. I'll be at the front pointing, going: "Haahaa!" when they get diphtheria or polio. Bloody morons..

I was raised in a christian-science household.
One of the BS practices of that cult is to not
have children immunized. I have never received
any immunizations or vaccines of any kind. I am
now 46 years old and I have never had a major
illness. I never get colds or the flu - ever! I am
one of the healthiest people I have ever known.
I'm not saying that we don't need immunizations
as a race, but as individuals, some may not need
them at all.

People who don't subject themselves to the small risk of immunisation benefit from herd immunity. When they stop to coo at the baby in the supermarket they'll share their disease. There still could be a place for public stoning in modern society.