You can be fired from many places for wrong kind of speech right now. That's not an issue of the USA, it's the issue of the employer. The government, as far as I know, did not mandate the firing, it only said that if somebody wanted to fire a teacher who is a fan of Joseph Stalin they don't have to let that person to indoctrinate their children but may let him go so he'd seek some other employment. And there was plenty of things supportive of USSR published in the US during the cold war.