The difference is dentists in the US cost money (unless you have a job with dental insurance which many low-end jobs do not). People who don't go to dentists regularly probably can't afford it. The Covid-19 shot is free (at least in the US).

Agreed. I doubt that half the population thinks that the COVID vaccine is a conspiracy to kill them, render them infertile, or depopulate the earth.

I'm not vaccinated, and I don't believe those things. I do see the dentist every 6 months though.

Tribal politics is probably a better predictor than fringe theories.

I have a friend who's gone off the deep end in the past year (like so many others).

He freely admits that he doesn't believe the vaccine is bad, and might even be good. His sole reason for not taking it is, and I quote, "because they want me to." In other words, simple spite.

We're not talking about a teenager here, but a successful man in his 60's who is probably the single most well-read person I know.

You see no value in the instinct to resist conformity? All major social and scientific progress has been made by someone with that kind of mindset.

You could argue that it's misplaced in this case, but that's already a more charitable interpretation of anti-conformists that will serve you better than just saying they've "gone off the deep end".