I would have a hard time defending McCarthyism. However, you may get some ideas from this article.
http://en.wikipedia.org/wiki/McCarthyism
Defend McCarthyism as appropriate for the time in which it occurred.
2 answers
It is a good technique to try to research arguments from both sides no matter your own views. It is also a good idea, as your question imples to put something in the context of the time when it occurred.
If you can get a copy Zoe Wannamaker's programme on the BBCs 'Who do you think you are' is good putting McCarthyism into context.
If you can get a copy Zoe Wannamaker's programme on the BBCs 'Who do you think you are' is good putting McCarthyism into context.