This is another atrocity to add to the war, and one that was unknown to me.
While it was true that many were members of the Nazi party, by mid-1933 it was the only party allowed in Germany. If one wanted a job, a career, study in university, or almost anything else in civil society, one had to join the party.
Since Jews only formed about 5% of Germans, most of the other 95% could join, unlike the Marxist-Leninist communists, who limited themselves to no more than 10% of the population.
For me, those who joined in 1933 onward had no choice, those who joined before did.