Then it all comes down to whether you want to discuss it with him.
If he regrets having been a member, he might welcome the chance to discuss it. And you'll have the opportunity to learn, first hand, how he came to regret it - - what changed in him and his life to turn him around.
Or, if he doesn't regret it, if he's still a racist, you've learned something equally valuable - - that you can be mistaken about people, and that people with horrifying politics can still seem like really nice people.
Interestingly enough, there's an article on the BBC site today that covers the same ground:
http://news.bbc.co.uk/1/hi/magazine/4734661.stmMy grandad the Nazi
Dan Tetsell grew up with an uncomfortable family secret - his grandfather was an SS officer. The more he's got to know about him, the more Dan realises his grandad was, in many ways, just an ordinary guy. And that's what's worried him.
(snip)
I don't mean a Nazi in the jobsworth sense. No, unfortunately, my grandfather Kurt Martens was in the Leibstandarte SS Adolf Hitler, the premier regiment of the Waffen SS.
Kurt was killed or went missing during the fighting around Prague castle sometime in early May 1945, so I never knew him. In fact, my mother was born a few months after his death/disappearance, so she too never got to know the man.
(snip)
A few years ago my mother uncovered a few rolls of undeveloped film that my grandfather had brought back with him while on leave from the front. They are a fascinating insight into a angle on the war we rarely see - the Waffen SS at play.
(snip)
Looking at these photographs it's impossible to avoid what one always hopes wasn't true about the Third Reich - these men are not monsters. No matter what sort of gangsters, charlatans and psychopaths they may have been following, the vast majority of the German people, even the vast majority of the Waffen SS were normal people.
In fact, my grandfather liked football and swimming, he seems to have been more normal than I am. And his two last letters home speak of a loving family man desperate for the war to end so he could return to his pregnant wife and young daughter.
And that, I suppose, is why I find this microscopic story of an insignificant part of the Third Reich so fascinating. If it shows that my grandfather can not only stand aside while bad things happen but actively take part, then it could happen to any of us. It's a lesson that's been taught again and again, but in this anniversary year it's worth hearing again.