Cointelpro ran into the 70's. Also you should read some Chomsky. Lots of examples of thought control.

A mixed-race or same-sex couple on TV? A quarterback mentioning racism?

The first has only become commonly accepted in the last decade or so. The latter is even more recent.

Well, there’s the example from the Twitter thread. But the point is that anti-leftist censorship and propaganda have been happening for a loooooong time.