When I read last month that voters in Portland, Oregon, had defeated a bill that would have fluoridated their drinking water, I was reminded of my first experience with an anti-fluoridation wacko. Jeffrey lived three houses down from me when I was a child. He was in his forties, lived at home with his mother, and did not work. I suppose that today he would be diagnosed as a highly functioning autistic. He was bright but very awkward. He liked my father, because my father was an intellectual, a lawyer, and a fellow Jew, and was kind to him. But whenever Jeffrey would walk away from our house, after my father had refused to sign another one of his anti-fluoride petitions, my father would close the door and sigh and explain that Jeffrey was insane.

Jeffrey’s politics tended toward Ayn Rand, Milton Friedman, the gold standard, and, on an especially bad day, Lyndon LaRouche. It was taken for granted in my house—and if any proof was needed, Jeffrey was—that only right-wingers were mad enough to oppose scientifically tested public-health measures. Only right-wingers would sacrifice children’s health to their own psycho-political neuroses. Besides, liberals fought important enemies, like war and poverty. Not fluoridation.

Today, of course, while the right still dabbles eagerly in the anti-fluoride, anti-vaccination, and other anti-science pathologies, the left may be the even greater culprit. Certainly the anti-fluoride coalition in Portland depended more on self-identified liberal voters than on conservatives. But there are key differences in how liberals and conservatives come by their fears. On the right, these mental illnesses stem from fear of government. On the left, their origins are a bit harder to pin down, but as I see it, they stem from an old mix of righteousness and the fear of contamination—from what we might recognize as Puritanism.

The new Puritans' anxiety is a threat to me and my children.

Let me give another example of left-wing Puritanism in action, one less glaring than the Portland referendum but which will be recognizable to many of you. Last month, at a birthday party for a three-year-old, I was hit with the realization that most of the parents around me were in the grip of moral panic, the kind of fear of contamination dramatized so well in The Crucible. One mother was trying to keep her daughter from eating a cupcake, because of all the sugar in cupcakes. Another was trying to limit her son to one juice box, because of all the sugar in juice. A father was panicking because there was no place, in this outdoor barn-like space at some nature center or farm or wildlife preserve, where his daughter could wash her hands before eating. And while I did not hear any parent fretting about the organic status of the veggie dip, I became certain there were such whispers all around me.

Like any moral panic, nobody was immune to its contagion. Soon, I was fretting—but for different reasons. For all I knew, some of these kids weren’t immunized, and they were fed only unpasteurized milk. The other parents were worried about germs and microbes and genetically modified apricots—I was worried about the parents. I was surrounded by the new Puritans: self-righteous, aspiring toward a utopian perfectionism, therefore condemned to perpetual anxiety—and in their anxiety, a threat to me and my children.