Although much has been made of the 'revelation' that Gunter Grass served briefly in the Waffen SS (and more has been made of the disappointment many feel at the hypocrisy of his concealment of that fact during a lifetime of serious political and moral writing, satirizing the hypocrisy of others while concealing his own), I would argue that a large part of the point of Peeling the Onion is that there are far more serious and damnable crimes than either the trivial "service" or the self-serving concealment of it.
Grass is ferociously critical (and contemptuous) of his younger self; time and again he shows his behavior as essentially selfish, self-centered, egotistical, and especially blind to both the love and sacrifices of others on his behalf; his portrayal of his efforts to "free" himself from his family background is not unfamiliar in portraits of young artists, but he shows himself both blind to the needs and feelings of his parents and sister, as well as unable to recognize or acknowledge their efforts to help him. We might conclude that he is constructing a portrait of the kind of artist who is so enclosed in the world of his creative consciousness that he cannot allow time for "normal" human feelings or relationships. Again, that is a familiar characterization, but his narration of his mother's death, in particular, portrays his own behavior as almost inhumanly remote and unfeeling. And yet, at the same time, we have constant signals that the feelings are there, beneath the surface, later to emerge in his art--and the suggestion that the art is, after all, more important.
The memoir, then, is simply not about his putative guilt or hypocrisy, nor is it really about his self-centered behavior; it is about the creative act and the ways in which the artist uses the matter of his or her life to create the art that justifies her or his existence. Grass is not really focused on how other people might "judge" his human relationships--his responsibility or lack of it, his parental or grandparental love and generosity, or the lack of it; whether his behavior fits our notions of how good people ought to behave is really not interesting to him, nor really should it be to his readers. No doubt a world full of Dr. Phils and Judge Judys will render their fatuous views in the latest psychobabble, but Grass (and his admirers) will be impervious to all that And those who read the book attentively (especially if they are familiar with his novels) will see that the constant references to the ways memory may trick us into taking a "story" for "reality" are really the point--not that there is no reality, but that our access to it is always framed by the stories we tell about it. Those who carp about his prizes or his literary eminence (and who suggest that the latter is compromised, the former subject to return) have not read, have certainly not understood, the artistic experience Grass has offered in this very fine addition to his great oeuvre.