CP's support of 1943 Smith Act trial against SWP Trotskyist leaders of Minneapolis Teamster's union was among most foul examples. Of course, government used law against CP leaders after WW2 (trial was in 1949, I think) which makes Julius Rosenberg's remark to his lawyer Emanuel Bloch even more tragic:
'This death sentence is not surprising. It had to be. There had to be a Rosenberg case because there had to be an intensification of the hysteria in America to make the Korean War acceptable to the American people. There had to be a hysteria and fear sent through America in order to get increased war budgets. And there had to be a dagger thrust in the heart of the left to tell them that you are no longer gonna get five years for a Smith Act prosecution or one year for contempt of court, but we're gonna kill ya!' (22 September 1953)
If Soviet Union had not existed after WW2, US would have invented it. Same goes for Ethel and Julius Rosenberg. Michael Hoover