It is a question which Harwood, a Jew raised in apartheid South Africa, asks of anyone who feels they can judge the behaviour of those trapped in totalitarian state.
Except that, in the case of Furtwängler, he was not trapped, but chose to stay. In Taking Sides, the job of David Horovitch's American Major Arnold is to find out why.
The fun here lies in pitting Horovitch's crude philistine against Pennington's imperious aesthete - then asking, who is the civilised one? Is it uncultured Arnold, haunted by the camps and bored by art, or is it the great artist Furtwängler, who according to the play, saved many Jews, though according to Arnold, served as a Nazi advertising slogan that said: "This is what we produce. The greatest conductor in the world."
In Collaboration, Harwood takes sides. The play is populated by figures only referred to in his earlier work such as Goebbels's sickeningly sycophantic culture minister Hans Hinkel (Martin Hutson) and, of course, Strauss, who Pennington portrays as an ageing and insecure obsessive, bolstered and bullied by Isla Blair's formidable frau.
Stauss's reputation as a Nazi collaborator is persuasively reassessed in the light of his Jewish grandchildren, and in particular his relationship with his Jewish librettist Stefan Zweig (Horovitch again), who, by killing himself in a suicide pact with his wife, collaborated more fully with the Nazis than Strauss ever did.
I suspect Collaboration will always work best as a companion piece to the more equivocal Taking Sides, which is strung through with the tension of an investigation.
But if, one day, a producer links Harwood's plays to Hannah and Martin, Kate Fodor's recently staged offering about Jewish academic Hannah Arendt and philosopher Martin Heidegger - the thinking man's Furtwängler - this absorbing pairing could grow into a fascinating season. Tel: 01243 781312
