Bonhoeffer?
This exaggeration is a overreaction (including the entire period) against like statements about Rome, but while the majority of both did not oppose Hitler (and the Protestant church was not a monolithic entity), there was resistance among relative few brave souls on either a doctrinal or moral basis. (Note, the German word for denomination is Konfession) But it is always a minority.
"At my first answer no man stood with me, but all men forsook me: I pray God that it may not be laid to their charge." (2 Timothy 4:16)
I think the below can help provide some balance.
The Protestant Church and the Third Reich until 1935
For the Soul of the People: Protestant Protest Against Hitler