[an_guy]

Why is it that whenever someone shares anecdotal evidence of their friend or family member being affected by a vaccine, the first response is mocking them for being against the medicine?

Suppose a commonly used drug caused severe reaction among a fringe group of people, you don't mock those people and call them anti-vax/unlucky. The pharma responsible for drug should look into the case and come up with guidelines for usage.

[OrvalWintermute]

I think it is because they are anti-medicine and anti-science

Good medicine, Good science are wonders of the modern world that have the possibility of doing incredible miracles for health and longevity.

It speaks to polarization and othering of people with different opinions.