Got your flame suit on? All connections checked? Good!On the one hand McCarthy wasn't too scrupulous about riding the wave of hysterical overreaction to the communist threat that prevailed in the early '50s.In the real world of politics, the truth is almost never "lying somewhere in the middle." The truth is usually the position the Republicans would like to take--if they didn't have to worry about the effect of journalism's PR power to get them unelected. So the Republicans trim away from the truth, partway toward the Democrat position.
The Democrat response to that tendency is, of course, to make their own positions all the more extreme to suck the Republicans as far from the truth as they can get away with.
That is the tendency in labor negotiations, too--which is why an arbitrator doesn't come in and automatically split the difference, but tells the two sides to come in with their most reasonable offer and warns that he will pick one offer or the other. So their offer had better be reasonable or it will not be compromised with but rejected. IMHO any voter who doesn't take that viewpoint is naive.
On the other hand a significant infiltration of government agencies, particularly The State Department, had in fact occured.
The question is, how much infiltration, and was the Truman Administration doing anything about it?The Venona transcripts, which the Army cracked secretly and against Truman's orders made it plain that Soviet agents were not just bumping into each other in the halls in the Roosevelt and Truman Administrations. They were working together, and hiring each other.
"The wave of hysterical overreaction" was actually an underreaction, compared to the actual threat revealed by Venona, which were secret from McCarthy and HUAC.