As you already know if you care about such things, Gunther Grass, so called conscience of post-war Germany, was in the Waffen-SS in WW2. Mr. Grass kept silent about this until he spilled the beans in his autobiography, Peeling Onions. On the one hand, this is Hitler's SS were talking about, on the other hand he was a draftee into a military unit.
Was it the crime or the cover up? Certainly keeping silent all these years only to reveal the truth in a memoir that would be guaranteed to sell like hotcakes is more than just "bad form". Really, how can you be a conscience if you can't admit the truth, and then only for personal gain?
Mr Grass certainly has his share of defenders, like Salman Rushdie and John Irving, and I'm certainly unboard with the view that his body of work stands indepently of himself (a view that allows me to see most movies and TV shows these days). So I don't believe the claim you should ignore a book because of the author's shortcomings. But Charlotte Knobloch, president of the Central Council of Jews, has a point when she claims thathis criticsism of his countrymen's inability to confront their complicity with Hitler is absurd when he can't confront his own -- but it isn't the criticism itself, it's Grass himself who becomes absurd. What is the difference between Bill Bennet and Gunther Grass?
Eamonn Fitzgerald points out that American records from his POW internment indicate Grass was a member of the SS, and the German press and biographers never bothered to look at them, even though the docoments are in the hands of a German organization in Berlin.