Disclaimer: I am one of the first to criticize others for making decisions about politicians' actions, safely esconced in different times and different circumstances from the politicians! So, I probably cannot go after Truman too hard, since he did have one or two other things on his mind.
I think the disclaimer points up some things that historians ignore about McCarthy, also. After all this was a time when people were SCARED--and rightfully so. Sputnik hadn't happened yet, but we HAD lost the nuclear secrets with Fuchs, the Rosenbergs, et al, and Stalin was seen as evil incarnate (which he was). So, to cast aspersions at McCarthy after the fact and divorced from the circumstances is ludicrous.