Hitler is not a very good example, because he is a person whose political significance so enormously outweighs his artistic significance that the latter is in effect nearly non-existant. Usually, any music with any quality worth speaking about is at least balanced in that regard. Of course, you always have to decide when the politics outweigh the art. You can’t just apply the same logic to Leni Riefensthal’s propaganda movies that you do to Morrissey or Paul Weller.
First paragraph: Quite so, but there is also a point here about the distinction between the artist as a person and what he creates. We are talking about what we can get out of someone’s records, not how we’d feel about him marrying our sister and turning up for the family christmas party every year, after all.

The point I am making is that I can’t see that there is any clear point in making a judgment of the person. “If that knowledge includes something that is, for you, beyond the pale then surely that will affect what you think of their art?” Yes, but not neccessarily by making me reject it. Take Knut Hamsun, to choose an example from literature. Supported Hitler throughout the German occupation, convicted of treason, published some truly inexcusable things including a glowing obituary for Hitler in the dying hours of the war. Which does not change the fact that he wrote the finest novels ever published in Norwegian. I love them unreservedly. Or Billy Bragg’s Between the Wars, in my frank opinion a remarkably stupid lyric that manages to list nearly all of the worst left wing staple idiocies of the past century within a three minute song, made by someone you know is all too capable of believing in them. But it’s still a great song, so great that you still feel the pull of the ideas because of the pure conviction with which Bragg delivers them.