This would be an interesting encyclical to take a look at. Do you know where a text of this encyclical can be found?
Interesting that Eugenio Pacelli talked Pius XI out of publishing this encyclical, and yet four months later Pius XI had a change of mind, and against Pacelli's advice, was going to deliver a public address anyway against the Nazis and their racial policies, putting in danger the 1933 Concordat. But he never lived long enough to do so.
What ever happened to that encyclical and the text of that address? Did Pius XII ever realize that the 1933 Concordat had been a mistake as his predecessor apparently did?
Can you point out the offensive parts on the Concordat? What exactly is the problem with it?