“I had the #Measles #Mumps #Chickenpox as a child and so did every kid I knew,” she tweeted, adding that her own kids were, regrettably, vaccinated. “They will never have the lifelong natural immunity I have. Come breathe on me!” Thanks but no thanks. I suspect my breath is better spent elsewhere.

A week and a half ago, a Republican state representative in Arizona said on her Facebook page that pressure on parents to vaccinate children “is not based on American values but, rather, Communist.” Bet you didn’t know that the original symbol of the Russian Revolution wasn’t a hammer and sickle. It was a syringe.

I shouldn’t joke, and I should add that anti-vaxxers run the political gamut. They’re on the left, their professed concern for social welfare proven hollow by the risk that their unvaccinated children pose to newborns and others who haven’t yet been — or can’t be — vaccinated. They’re on the right, among people who see the government and its edicts as oppressive forces. Paranoia has no partisan affiliation.

I should also add that alternative facts had currency long before Kellyanne Conway christened them such and that junk science, nutty hypotheses and showy apostasies have been around forever. Humans aren’t rationalists. We’re romantics, and the world is wondrous when you believe that you belong to some brave and special tribe and have experienced enlightenment — about the assassination of John F. Kennedy, about the existence of extraterrestrials, about the 9/11 attack on the World Trade Center, about vaccines — that all the less perceptive, more gullible conformists out there simply can’t comprehend.

But there are differences now that make the cranks that much more baffling, numerous and pernicious. For starters, they fly ever more stubbornly in the face of sophisticated research and hard-earned knowledge. Beneficiaries of wisdom that prior generations lacked, they toss it away, wasting and mocking progress itself.

At the same time, in many educational circles, there’s as much talk of students’ individual truths as of the truth. Joan Donovan, the director of the Technology and Social Change Research Project at Harvard’s Shorenstein Center, said that social science and history courses increasingly emphasize that truth is situational and that “very few things are always true all the time.” That healthy skepticism can turn unhealthy when it leads to the rejection of incontestable realities. There’s “a crisis of authority, a crisis of expertise,” Donovan told me.

There’s also a man in the White House, at the Resolute Desk, who makes grand pronouncements based on random conversations; implores Americans to distrust traditional institutions and conventional sources of information; and promotes conspiracy theories (millions of illegal votes, a celebration among Muslims in Jersey City on 9/11, and on and on). He has specifically echoed and validated the apprehensions of anti-vaxxers. Whether he’s symptom or cause doesn’t matter. He’s dangerous either way.