Oh, the righteous indignation: "Horowitz is compared to a former Nazi? " Would you forgive someone who exerted as much effort for a Nazi cause in the US as Horowitz did for Communism in the US? Time, effort, skill level, etc. The comparison is not exact because whereas Communism was a very real internal threat to the US nazism was not. Not very many 'swatsika diaper babies' running around.
I don't know that he did any damage. I do know that he is now doing much good.
Wonder if you feel the same way about Whittaker Chambers?