I’m not sure if this is true. I think there has always been restrictions to free speech, it’s just what’s not allowed has changed over the years. Try having pro Soviet material in the 70s.
I guess it depends on what you mean by "pro Soviet material" but Academia and adjacent fields were full of USSR sympathizers in the 70s. People like Marcuse were/are very influential figures.
Marcuse was a communist but not pro-Soviet by most measures.
Academia did indeed have quite a few Soviet sympathetic figure. Tbh, I'm not sure why the gp picked the 70's. The cold war was mostly thawing then as the failure of the USSR was becoming visible (though Reagan partly reignited it in 80s). The 1950s was a period where real and suspected sympathizers of the USSR were drummed out of their positions in academia, entertainment and elsewhere. The witch hunts died down in the 1960s as US society relaxed a bit itself.
