Bill Ayers and his wife Bernette Dohrn were promoted and mentored to positions of power by people of my father's generation ( born 1913). These two were **known** and self-confessed terrorists.
The rot was in place long before the 1960s. Joe Mc Carthy was right!
You are right and it was in place even before the '50s.
However I believe that as I understand David Horowitz explain the emergence of the New Left it was never so radical and violent as the 1960s. When word of Khrushchev's 1956 revelations about the real Stalin reached America it turned many American Communists away from the CP/USA and many "red diaper babies" rejected all but the most revolutionary versions of Communism. Thus the New Left.
I recall both McCarthy and the 60s when the MSM gushed admiration for the demonstrators as the most intelligent generation ever.
This oft-posted cartoon shows the rot in the '30s.