This is supposed to be some kind of revelation?
Here's a bit of people's history for you younger people here.
The hippies themselves promoted pot smoking as a way to make people more leftist (as they conceived the notion of "left" anyway) because it "mellowed you out" and made you led "uptight" like the "straights"** were. As a high-schooler in the early 1970s, I was part of a picked-on minority of straights who didn't smoke pot. And I was proud to be even more radical left than the freaks*** without smoking pot.
So of course everyone back then understood that Nixon's "War on Drugs" was an attack on the hippie left.
But in 1976, I realized that whole cultural association of pot with the left was coming to an end when, in October, a roommate from Princeton, NJ who smoked a lot of pot yet was a straight "preppie" looking type decided, over a doobie, to vote for Gerald Ford, not Carter, for president.
** "Straight" - The term for a well groomed, neatly dressed, non-pot-smoking person with conservative political views. It was generally derogatory. It did NOT mean "heterosexual". Queers ("gay" was not invented yet) and anyone remotely suspected as such, were feared and reviled by freak and straight alike.
***"Freak" - The term for long haired, bearded, pot smoking, ragged jean or Oshkosh-bgosh overall-wearing, sexually licentious countercultural types - it was not at all derogatory.