My personal observation on this issue.
While we could get emotional and say, what was little Hans guilty of to get expelled? Let's comemorate his plight. Well, we are also comemorating his uncle Fritz's plight, who may have not been so inocent.
Operation Tannenberg (German: Unternehmen Tannenberg) was the codename for one of the extermination actions directed at the Polish people during World War II, part of the Generalplan Ost. Conscription lists (Sonderfahndungsbuch Polen), prepared by Germans already before the war, identified more than 61,000 members of Polish elites: activists, intelligentsia, scholars, actors, former officers, and others, who were to be interned or shot. Members of the German minority living in Poland assisted in preparing the lists.
In the interwar period German minority organizations in Poland such as Jungdeutsche Partei, Deutsche Vereinigung, Deutscher Volksbund and Deutscher Volksverband actively cooperated with Nazi Germany through espionage, sabotage, provocations and political indoctrination. They maintained close contact and were directed by NSDAP, Auslandsorganisation, Gestapo, SD and Abwehr. It is estimated that 25% of the German minority in Poland were members of these organisations.
By October 1938, SD agents were organizing Selbstschutz in Poland. Ethnic Germans with Polish citizenship were trained in the Third Reich in various sabotage methods and guerilla tactics.
Polish historians estimated that the majority of approximately 50,000 Poles killed in the early days of the German occupation were victims of Selbstschutz.
The total number of Selbstschutz members in Poland is estimated at 82,000.
The existence of a large paramilitary organization of ethnic Germans with Polish citizenship that helped in the German war against Poland and engaged in widespread massacres of Poles served as one of the reasons for the expulsion of Germans after the war.
It is worth mentioning that Katyń was a similar action on the Soviet side thanks to the NKVD-Gestapo cooperation.
So, the plight of German expellees is an issue to some Germans, but we can see how the Polish side has a bit if a kneejerk reaction. Erika Steinbach, the leader of this movement, was born in occupied Poland to a German soldier. Is she an expelee?
One last thing. The process of expeling the Germans from Poland after the war was conducted by Soviet controled People's Poland. who also proceeded to round up Polish Home Army soldiers and often executing them. Their crimes are unpunishable to this day, but that's another story.
When are we going to see spellcheck on PF? :)