For clarity, I am copying below, the final paragraphs from the article by Dr. Haynes where Haynes analyzes the 159 names cited by McCarthy at various times and compares those names to Venona documents and other sources.
http://www.johnearlhaynes.org/page62.html
This should put the matter in proper perspective:
“Security Risks
Of the 159 persons listed above, there is substantial evidence that nine assisted Soviet espionage against the United States: Lauchlin Currie, Harold Glasser, Gerald Graze, Standley Graze, Many Jane Keeney, David Karr, Robert T. Miller, Franz Neumann, and William Remington. David Zablodowsky is a tenth ambiguous case.
Some of the others were security risks. To say that someone was a security risk is not to say that that person is a proven or even most likely a Soviet espionage source. It is only to say that in matters of national security “better safe than sorry” is a principle. Risks should be minimized by excluding those persons from employment in positions where they would have access to sensitive information.
Risk factors vary from the purely personal to the ideological. Entirely patriotic and loyal persons may have risk factors that make them a security risk. Someone with a history of financial irresponsibility (chronic gambling, bankruptcy) may be tempted by financial gain to betray secret without regard to their patriotism. Someone with close relatives living in a hostile foreign nation may be vulnerable to blackmail due to coercive threats against those family members.
And, of course, someone with ideological sympathy for a hostile foreign power may be tempted to betray by appeals to that ideology. Obviously, in the Cold War between the Communist bloc and the West, persons with Communist or pro-Communist ideological sympathies were security risks due to the possibility of ideological recruitment by Communist intelligence officers. Indeed, the great majority of American, several hundred, now known to have assisted Soviet espionage in the United States in the 1930s, 1940s, and 1950s were motivated by ideology and many were secret members of the CPUSA.[54]
Many, but certainly not all, of those in the above lists had in their background some ideological security risk factors. A few were established as having been members of the Communist Party, USA (CPUSA) or the Young Communist League. Many had belonged to a number of special purpose organizations, some closely, some not so closely, aligned with the CPUSA, were know to former co-workers as pro-Soviet, or had other signs of Communist sympathies. In some cases those affiliations were recent or ongoing. Frederick Schuman, for example, had a long and enduring history of intense Communist sympathies. With others, however, their affiliation with the Communist left were youthful and a decade or more in the past, and the person may have abandoned those views. Stephen Brunauer, for example, had been in the Young Communist League in the late 1920s but appears to have abandoned the movement by the early 1940s and in 1946 the U.S. government sent him to Hungary (he was Hungarian born) to assist in the escape of Hungarian scientists from Communist Hungary. There were also cases were some association legitimately raised security risk concerns but on inspection, the association appears to have been coincidental. For example McCarthy number case # 1 (Lee list # 51) Herbert Fierst, socialized with and was associated at work with several persons known to be linked to Soviet intelligence. But on examination, Fierst’s association appeared to have been no more than that: social and related to his official duties. Among other points, he was a firm supporter of Zionism, an ideological attribute not merely distrusted but hated by Soviet intelligence.[55]
It would take an extensive review of each person separately to come to a firm view on each case, and in a number of cases the passage of time might make reaching a firm conclusion impossible. My own view is that a number of those on the lists above, perhaps a majority, likely were security risks, but others, a minority but a significant one, likely were not, and some, Drew Pearson, Dean Acheson, and George Marshall for example, certainly were not.”
And Senator McCarthy never claimed that Drew Pearson, Dean Acheson, and George Marshall were in any way supporting Communism — but their actions minimized the problem and made it easier for the Communist moles to do their work.