You should try reading “Witness” by Whittaker Chambers if you really want to lose some sleep at night. He was one of them.
I already read Chambers’ book, before I read I read, Blacklisted by History.
They are almost sequential.
If you think that the Chambers’ book is scary stuff, read Blacklisted by History.
I swear there is no way that Roosevelt could not have known what was going on. In the Chambers’ book, he mentions that he went to the home of some government official and told his whole story about the communist infiltration of the US government, and that the man called Roosevelt before he ever left the house, and nothing came of it.
One thing that I learned from the Chambers book was that the Communists are extremely anti-Christian and that members of the communist party are explicitly forbidden to attend church.
I found this interesting because the CIO reported my grandfather to the HUAC as a communist and the FBI proceeded to destroy his life. They had to have known that the charges were false because my grandfather was an elder in his Methodist church. He and my grandmother were both very active in the church and the FBI interrogated all the church members as well.