Also, back in my day, in trying to get a security clearance, if you even had a casual friend who was a communist, they would look very closely at you, and it could be used to deny you even a "Confidential" (the lowest level of security clearance). And yet Brennan, who is an actual Communist Party voter (and a Muslim Convert, but that´s a whole different story) gets the highest level of clearances, and gets to be head of the CIA.
You make perfect sense!
Look at who was doing the hiring at cia back then and you will find the answer.