An interesting article. I do believe there is a difference between depicting something and endorsing something. Obviously, whether that depiction is done in a manner that enables them to succeed or fail as a musical artist is a question only the listener can answer. And those answers are bound to differ based on personality, temperament, background, culture, age, religious belief, and a vast array of other factors. The answers may also change over time (an opinion on a piece of music is not a blood oath).

To get to specifics:

1) Eric Clapton - Never been a huge fan, and don't know enough about this issue to comment.

2) Rolling Stones/John Lennon - I don't think there was any racist intent whatsoever, quite the opposite. However, despite having their hearts in the right place, both songs seem misjudged or unnecessarily flippant today.

4) David Bowie - I'm a huge fan. As someone else here commented, his interest in Nazi occultism was brief and not an interest born as a result of agreement with any of Hitler's insidious beliefs. Indeed, Bowie's anti-racist actions, especially throughout the latter part of his life, refute that position entirely.