Some remaining thoughts from readers:

As a historian of modern Central Europe, I've been following your discussion of President Obama's unfortunate use of the term "Polish death camps," a widely-used term that understandably infuriates Poles.  As other readers have already pointed out, there existed no collaborationist government in occupied Poland as there did in other European countries (and not just in Eastern Europe; see Vichy France and the Quisling government in Norway); there was no Polish division in the SS; there existed in the Polish Underground State a resistance movement of a kind not seen elsewhere; and there were many Poles who did help their Jewish neighbors, resulting in more Poles being recognized as "righteous Gentiles" than any other nationality. 

At the same time, the Polish resistance did relatively little to assist Jews.

There were Poles who hunted Jews and turned them over to the Nazis; there were Poles who profited from the round-ups of Jews by seizing their property; there were Poles who exploited Jews on the black market and/or by demanding payment not to denounce them; and there were Poles who murdered their Jewish neighbors, both during the war (e.g., Jedwabne) and after (e.g., Kielce).

In assessing all this, though, it is worth remembering that Poland was subjected to a far harsher Nazi occupation regime than France, the Netherlands, or other Nazi-occupied territories.  It also worth remembering that for the first two years of the war, the Poles were subjected to two different occupation regimes, with the Soviets occupying eastern Poland and subjecting the Poles there to Soviet brutality.  Indeed, understanding that experience of occupation and its effects on the fabric of social life is necessary for understanding the Jedwabne massacre; as Jan T. Gross himself points out, far more than simple antisemitism was at work.

Finally, our memory of the Holocaust is complicated by the fact that the Nazis located the death camps in occupied Poland.  As a result, when we visit those sites of genocide – those cemeteries – we travel not to Germany, but to Poland.  That, combined with Poland's own troubled history of antisemitism (not unique in Europe, by the way), often leads people to ascribe to Poles far greater responsibility for the Holocaust than is ascribed to other Europeans. 

I wonder what the response would have been had President Obama referred to the concentration and transit camps in Nazi-occupied France and the Netherlands as "French concentration camps" and "Dutch concentration camps."  That people don't use such terms speaks to the ways in which we often associate the Holocaust with Poland, which only then strengthens the Poles' own (defensive) tendency to view their wartime history as a heroic story of national resistance.  We need to complicate both of those narratives.

Another reader:

I am the son and grandson of Holocaust survivors from Poland, and I’d like to give you a bit of family history. My pregnant grandmother and her entire family were not initially interred by Nazis, but by the local Poles – THEIR NEIGHBORS – who handed them over to the Nazis. After the war, when they tried to return to Poland, my grandmother’s younger brother was killed – again, by the Polish neighbors – and the rest were chased away to a displaced persons camp.

Just to be clear: my great uncle survived Auschwitz and was murdered by an angry mob of his own neighbors. The Poles who did help and hide Jews were also singled out for punishment. While this was going on, the Church, perhaps the only institution that could have stopped the mob, did nothing.

To me, it is obvious that the outsized reactions from Poland is a manifestation of societal guilt and a desire to whitewash their past.