Couple examples would be
saying 1 in 3 kids have diabetes (not even close)
thimerosal in vaccines today causes autism (it was removed almost 30 years ago for children)
Discussion
Crazy thing is, the guy who started the entire vaccine autism thing admitted under oath that he faked the data in the study and the study has been retracted.
Fake data and we still changed the vaccines and people still believe it is an issue.
There is nothing that will change their minds. Unfalsifiable belief.
If you simply say that every fact you dislike is part of a coverup of your preferred narrative you completely detach your thinking from objective reality.