Why? What has his conductorship have to do with his political ideology?
Feeeeeeeeeeelings is what often gets us into trouble.
Genius, whether communist or fascist or whatever, is still genius.
Art, especially music and poetry, are about feelings. Music without feeling is just mathematically measurable noise. So why do people with such venal feelings as Wagner and Von Karajan become great musicians? Why were the two greatest influences on modern poetry, Pound and Eliot, fascist sympathizers? It makes one wonder about the validity of art. Is it just some pagan venting of feeling?
Of course Field Marshall Radetzky is politically incorrect anyway, since he won victories for the Habsburgs over the Italian revolutionaries in 1848.
Just as we at FR get unhappy when artist like Speilberg endorse obama, it makes me unhappy when artists like Von Karajan endorsed hitler.
Artistic Genius does not guarantee political or even moral rectitude.