Thucydides, I absolutely agree with you. I just saw the movie today and I had the same impression the entire time that Tarantino was poking fun at a Western audience that is reflexively repulsed by Nazi's.
Christoph Waltz' character's monologue about the nature of the rat I thought was clearly in reference to this theme. He points out that we have a reflexive disgust of rats though they have never done us any personal harm, and while he's talking about the Jews, I think Tarantino is talking about Nazi's. The Frenchman is apt to point out that rats spread disease, just as we might point out that the Nazi's carried out a most disgraceful genocide, but Christoph Woltz is quick again to point out that the Bubonic plague was a long time ago and that squirrels are just as apt to spread disease as rats, they are both rodents, yet we do not treat squirrels with the same reflexive disgust as we do the rats. Again I would say that the point is that most of us have a reflexive disgust of Nazi's that goes beyond the normal revulsion of other groups that commit genocide or other murderers and killers, and some are revered as war heroes. Tarantino makes this connection with the German war hero who's deeds we naturally see as atrocities, though we might laugh at the horrific cruelty committed by Brad Pitt and his band of Inglourious Basterds.
It was clear to me that Tarantino was going out of his way to show the more human side of Nazi's, to make it clear that they are just as human as the Allies. As Thucydides mentioned, one of them had just had a son and was celebrating with his friends, even playing drinking games similar to ones that we would play. Also near the start, a Nazi's courage and discipline in the face of death would have been highly commendable if it had been a Yankee in his place, and his consequent bludgeoning would have been far more traumatizing if it weren't so easy to rationalize his fate with his antisemitism. The German war hero makes another humanizing statement in passing as a joke, pointing out that "most" German soldiers are somebody's son. I thought it was quite obvious that all these details were there to highlight the double standard between rat and squirrel, though they may both be rodents.
Draugnar, I think the comparison between the theatre of Germans and the audience is a valid one. Yes, you might be able to rationalize the horrifying brutality committed by Brad Pitt and the Inglourious Basterds (we're not talking about Ahhhnold here), but it is just as much a portrayal of WWII and actual people dying as the embedded film within the film of the German war hero was a portrayal of WWII and actual people dying. The difference is merely which side of the us vs. them it's on. It would be foolish to pretend that the Allies didn't also have blood on their hands, but as the victors they are celebrated as war heroes rather than war criminals. I'm not vindicating the Nazi's in any way, but I feel that the mere fact that I have to say that as a disclaimer is a testament to the reflexive cultural repulsion held for WWII Germany.