McCarthy was both good and bad. There was certainly the potential for Communists to infiltrate the U.S. Government and there was evidence that they had. On the other hand, McCarthy acted like a Communist trying to make his ends justify his means.
Yeah, that's pretty much it. But I'm pretty disfavourable to McCarthy, his supporters over-estimated the DOMESTIC Communist threat, I think. And the means were pretty awful...people like McCarthy might actually have lost the Cold War, at least idelogically.