The dispute over whether Pius "spoke up" centers around the cultural differences between how Catholics and Protestants address sin. If there's one thing that Reformed Protestants are known for, it's their belief in creeds and confessions. And in general, Protestants believe that each person has a responsibility to "make a good confession" and speak their faith publicly, no matter how difficult the circumstances or bad the anticipated response (e.g. Luther's "Here I stand, I can do no other", etc.). I suspect that many see the choices as martyrdom versus cowardice, the measuring stick used being words spoken, and very little middle ground is granted to the silent.
Now consider that Pope Pius XII made few, if any public statements, condemnations, or anathemas against National Socialism, the Nazi Party, or Hitler specifically by name (to be sure, public statements, pronouncements and sermons were made, but no names were given). It's this failure to take a public, verbal stand that is IMO at the heart of many accusations against Pope Pius XII. Some people (Protestants as well as Jews) don't think Pius XII spoke out loudly and pointedly enough against Hitler. They believe that, if the Catholic Church really were as powerful and influential as it's adherents claim, that such actions by the Vicar of Christ would have changed the course of the war.
Critics have read all manner of cowardice, antisemitism and other evils into the (in)actions of Pius XII, based upon his perceived silence as the Vicar of Christ towards Hitler. Did Pius XII save a lot of Jewish lives? I believe so. But IMO the better question is, what could the Catholic Church have accomplished, had the Vicar of Christ openly denounced Hitler?
The same thing that the Dutch bishops accomplished by openly denouncing Hitler . . . an immediate roundup and execution of the local Jewish population.
But Time magazine, Golda Meier, and Albert Einstein seem to think that he spoke out . . . even if in somewhat veiled words. And Mit brennender Sorge (authored by Cardinal Pacelli as he then was, but issued by Pius XI) is not veiled at all. It names names. And it made the Nazis extremely angry at Pacelli . . . they didn't think he was silent. He was condemned roundly and nasty cartoons were published about him in der Sturmer.
And the Nazis further responded (once they had control of Italy) by attempting to round up Roman Jews, and by attempting to kidnap and assassinate Pius XII. The local German Army commander talked Hitler out of it, but it was a very real risk.
For your answer to that you need to look no further than the People's Republic of China's "official" Catholic Church today. In case you hadn't heard, the Nazis were all about propaganda, and good things seldom happened when their feelings got hurt. The major religions in Germany today are Lutheran and Anglican, I believe. The correct question may be that if Protestant's "can do no other" than to speak out, why didn't millions of them end up in the camps? Because this lame argument, like all the others, has always been first and foremost a politically correct way for the left (and people who just hate Catholicism) to attack the Catholic Church.
The Pope did condemn Nazi racism, and back in 1942, when the Nazis were the sdtrongest power in Europe, the NYT gave him create for doing this, in contrast to the silence from the Western Powers. And it is ironical that you should mention Luther who is famous for his anti-Jewish diatribes. But as for the effect, you see how the American Church “obeys” the pope’s teaching om birth control and abortion. There were many, many “good” German Catholics who were willing to follow “Der Fuehrer” wherever he led and felt that the Jews were gerting what was coming to them. Pope Pacellit knew the Germans. The famous Concordant concluded with Hitler was the best they he could, as secretary of state, get with the Nazis after the German bishops announced—against Pius’ XI’s wishes — that it was OK for Catholics to join the Nazi Party. That nation unity thing, you know. That Catholic thing was just a private matter, you know./sarc.