When the pope did speak his address was long - 45 minutes - and delivered in his usual manner of general comments on the current situation within the broad context of Catholic teaching. It is important to note that what the pope did say as opposed to what he did not say was still of value. In his role as Chief Pastor of the Church, the pope did outline Catholic teaching and offer a way forward based on principles of natural law and Thomistic theology.
The oft-quoted section has to be seen within its context. It comes at the end of the speech and is part of a cry for the voiceless - victims of aerial bombardment, widows, orphans, the countless dead and those condemned to death on the grounds of nationality or race.
Pius did not name names, but the Nazi regime listened to the broadcast and heard it as an indictment of National Socialism. The British and Americans heard it and declared it a condemnation of German atrocities, although privately they expressed reservations that it was likely to be the best they would get. The Jews of Europe most likely did not hear it or any of the other victim groups for that matter. Nonetheless, the pope did say something - it may not have been explicit enough for many, but it was a statement nonetheless.
Arguments over the text have gone on for decades. The principal complaint is that the pope's moral duty was to speak out clearly and unambiguously, naming the murder of European Jewry as a crime beyond any other committed in the war so far. The counter-argument says that Pius was painfully aware of the situation and feared making things worse by naming the extermination process in clear terms.
My understanding of the events leading up to the 1942 Christmas address is that Pius was caught in a very difficult situation. The outcome of the war was by no means decided in December 1942 although hope for an Allied victory was becoming something more than a dream. What causes me to lean towards a more negative assessment of the Christmas address lies in the Allied Declaration made a week earlier that named the slaughter of the Jews as a crime for which Germany would be held accountable. In that respect the Allies had named the crime explicitly - it was secret no more.
Pius believed that if he condemned the crimes of one side he would be obliged by papal neutrality to condemn the crimes of the other side as well. It is competently arguable that Pius had a clear idea of crimes committed by the Soviets in Eastern Europe, especially in the Baltic States and eastern Poland and that he worried about what would happen to the Church "in the East" if he named or suggested one of the Allied powers to be as guilty as the Germans of atrocities.
In any case the Christmas message of 1942 was as far as Pius XII believed a clear statement against atrocities in general and the extermination of the Jews in particular.
The text is posted in the "pages" section of the blog.