Can youth and the forces of history be cited in Grass' defense?

 Does he Gunter Grass, his Nobel Prize being revoked, and his book The Drowned and the Saved. Also the book Peeling the Onion is involved.
In August of 2006 Gunter Grass revealed to journalists that he was a member – albeit a youthful member – of the WaffledC XXX SS, a paramilitary extension of the Nazi party deemed a criminal organization by the Allied judiciary at Nuremberg. The outcry was enormous. Among other things it was suggested that the Nobel Prize bestowed upon Grass be revoked. Having read Peeling the Onion decide, to whatever extent possible, if Grass, by his own admission, is answerable to the accusations made by Levi in his The Drowned and the Saved, those Levi directs against “average” Germans. Can youth and the forces of history be cited in Grass’ defense? make any sort of effort on his own behalf to excuse his conduct during the war? Is his account believable? Please cite from the two books above.