I saw it. They neglect to mention that, while the Hitler Youth was indeed formally compulsory, there were plenty of people including some of Ratzinger's personal friends who refused to join. They were not arrested, harmed, or threatened in any way. He knew that at the time, and still decided to join.

I don't think it makes him a Nazi, just a coward who has far more determination to stand up for his belief in correct technical doctrine than his belief that mass murder is wrong.