The material taboo
Haven't discussed this lately ... Stuttaford at NRO
mentioned the switch of the 'organic food' fetish, or the cargo-cult style of concrete religious thinking, from Right to Left. This happened fairly quickly, I'd guess around 1970. The 'organic' fetish includes a perfectly standard and predictable set of taboos:
Hates fluoride in water
Hates pasteurized milk
Hates tobacco and alcohol
Tends toward vegetarian, not always total
Favors 'organic' or 'health' foods
Loves exercise, especially mass calisthenics
These were an intrinsic part of Hitler's program, and they came from an earlier German hippie-like movement (die Wandervogel).
From 1945 to 1970, you could predict with about 75% certainty that an American who held these preferences would be a Bircher.
Consider the right-wing general in Dr Strangelove, constantly afraid that Commies were "preverting his vital bodily fluids." Only slightly parodied: the Birch types really did talk that way.
After 1970, you could predict with about 75% certainty that a body-purity fanatic was a Commie.
The taboo switch corresponds exactly with the official switch of American Leftism from the universalist Marx to various forms of Fascist-derived identity politics in 1968. The taboos came into the Left from hippiedom, not from the Birchers. Just as they had come to Hitler from the Wandervogel, not from prissy monarchists.
I don't think the two changes were ever considered as a package. Ideological leaders of the New Left, like Frances Fox Piven or Allard Loewenstein, never thought about milk and vaccines. The Body Purity Syndrome just naturally fell into place, which indicates that it's an automatic companion of identity-style thinking.