Actually, I think the 60s saw the rise of radicalism. Liberalism was already the dominant political force, and had been since the 1930s. However, it took a few decades for the liberalism of the government and academia to corrode the popular culture and transform itself into a radical attack on the prevailing American morality.
It's like once he was killed, young people were encouraged to act out, to demand, to believe that they were owed something because he was lost. The libs just twisted everything around. He would have been appalled. No wonder Teddy always has a cow when Rush plays some of his brother's old speeches. Can't be reminding the people of MA just how far he has strayed from his brother's principles.