What was he right about? That Russia had spies in the US and was actively recruiting others. That was always the case and will forever be.
" "McCarthyism" as "the practice of publicizing accusations of political disloyalty or subversion with insufficient regard to evidence" and "the use of unfair investigatory or accusatory methods in order to suppress opposition.""
That's about as unamerican as one can get. All of the people on his list, which actually did not contain any names but only case numbers, came from internal State Department security which was investigating them. McCarthy just used "threat of communism" to become more powerful and with more power, more corruptible.
I know some would like to ressurect him, but he is way too deep to do that.
And if you read some of those declassified documents, you will find contradictory and unsupported allegations. Check out
http://en.wikipedia.org/wiki/Owen_Lattimore
http://foia.fbi.gov/foiaindex/owenlatt.htm
as an example.