I've had a creationist tell me that evolution can't be real because he found out that DNA means "Deoxyribonucleic acid" and that an acid would just "dissolve" the body and therefore he "knew" that DNA wasn't real.

I've had a religious flat Earther tell me that the Earth isn't round, it was just created by God like a pacman level where if you go too far in one direction you appear in the other end "so you can't escape".

I wouldn't be so sure to think that people who think that gut bacteria is bad don't exist.