Resistance was possible
The new pope, Benedict XVI nee Cardinal Ratzinger, has said that his participation with the Nazi's Hitler Youth program was entirely nonvoluntary, and that resistance to the Nazi regime was impossible.
This is false. From a blog called Is That Legal? (found via Brian Leiter):
Now, just to be clear, I'm not saying that Ratzinger's Nazi past makes him an evil person, or that his election as pope is tantamount to giving the position to Goering or something. I'm just saying that we shouldn't pretend that his cooperation with the Nazis wasn't a choice. That's all. It may be an understandable choice, an excusable choice--but still a choice.
... even during times of (officially) universal [Hitler Youth] membership ... there were always some reflective adolescents of both sexes who were different. They protested against the stifling rigor by refusing the state's youth conscription. . . . One boy in northern German Rendsburg, supported by his father, risked total confrontation with his leaders simply by growing his hair long ... Peter Wapnewski, later a professor of German literature, as a youth was hypnotized by American jazz and swing and thus forged a doctor's letter to stay away ... A particularly sensitive girl in Hamburg risked expulsion from the BDM [female equivalent of the Hitler Youth] because she found its views to be drivel ... The noted Hitler biographer Joachim C. Fest, who even at seventeen was a critic of the Fuhrer and his Nazi regime, had never bothered to join [Hitler Youth].
In evaluating someone's moral character, you must examine the choices they have made. All of us will have made good and bad choices, but it is immoral and immature to try to hide those choices, or to pretend that one had no choice.