Riefenstahl definitely knew what Hitler and the Nazis were about. Mein Kampf was first published in 1925 and was required reading after his 1933 election. His speeches made no secret of his master plan for the "master race".
But IIRC (and I might not - it's been many years since I saw the film) while Triumph of the Will was heavy on the Nuremberg rally's militaristic themes of power and strength, the film never actually depicted violence. No question, it was extremely effective in manipulating German feelings of resentment and vengeance, but to what extent is she responsible for the actions her work helped inspired others to commit? Would they have behaved differently in the absence of people like Riefenstahl and Goebbels? Intriguing question.
Wagner is definitely a controversial case. His music is for all intents and purposes banned in Israel because of his vicious anti-Semitism, but many prominent Israeli musicians have argued that his artistic genius should be regarded as distinct from his beliefs. As you can imagine, this is a sensitive issue for the many Holocaust survivors living in that country.
(While we're at it, we can add writers H.L. Mencken and T.S. Eliot to the list of highly-regarded intellectuals who were also well-known for their anti-semitism.)
What about Elia Kazan, director of Streetcar Named Desire, On the Waterfront etc, who "named names" to HUAC (the House equivalent of the McCarthy hearings)? On one hand, the people he identified WERE communist sympathizers, many of them operating in secret, but their careers were destroyed as a result of their personal beliefs, which contradicts our notions of liberty. Should we still watch these classic movies? Should he receive awards recognizing his cinematic achievements and contributions?
I disagree that what happened netween Chris Brown and Rihanna is a private matter. Cheating is one thing, brutal violence are another. They are very public celebrities, who enjoy all the perquisites of fame, and as such they serve as role models for their fans.
Definitely a thought-provoking question, Dedachan. Thank you for asking it!