The fact that Ratzinger was a Hitler Youth isn't that disturbing, I think, because all German boys were required to be, and it isn't his fault that he was a boy in Germany at that time. Many people who were Hitler Youths went on to be vocal opponents of the Nazis. The fact that Ratzinger also served in the German army during the war is more disturbing, though he was evidently in an anti-aircraft unit and therefore almost certainly not involved in any atrocities.

Ratzinger's status as an ultra-conservative Catholic is much more disturbing to most people, I think. I mean, seriously--Catholics are generally much more concerned with how the Church deals with Catholics than how it deals with Jews, and that's hardly surprising. I think Ratzinger is going to have a lot of work to do if he expects to receive the same kind of respect from the Jews that his predecessor did, but that would be true even if he weren't German and an ex-Hitler Youth.