He had no choice

Ratzinger's family, especially his father, bitterly resented the Nazis, and his father's opposition to Nazism resulted in demotions and harassment of the family.[20] Following his 14th birthday in 1941, Ratzinger was conscripted into the Hitler Youth – as membership was required by law for all 14-year-old German boys after March 1939[21] – but was an unenthusiastic member who refused to attend meetings, according to his brother.[22] In 1941, one of Ratzinger's cousins, a 14-year-old boy with Down syndrome, was taken away by the Nazi regime and murdered during the Aktion T4 campaign of Nazi eugenics.