Eartha Kitt was on his list?! WTF did she do? I skimmed through her Wikipedia page, and the only thing I could see was that she was an activist in helping underprivileged inner city kids, and she called out politicians for not doing more to help them as part of that work.
I don't know the specifics of why Nixon thought Eartha Kitt was an 'enemy.
Nixon got his start as a Congressman on the House Un-American Activities Committee. He was doing the same thing as McCarthy was doing in the Senate, and as a California boy he was tuned into Hollywood.