Charming - i guess your DP's family were ethnic Germans? Does your DH know if they signed the Volkdeutsche register? I don't blame them if they did - the alternative for ethnic Germans in occupied Poland was a concentration camp if they refused to sign the register. If they signed it then the Polish Underground considered them traitors. Very difficult & i don't know what i'd have done in that position.
It's wrong & sad that because of the actions of the Nazi Germans your DP's family were forced to leave their ancestral homeland.
I have German Jewish ancestry & Polish friends from Silesia.
I know that i hate many (not all) Nazi-era Germans because I know that but for the RAF's bravery my Gran's family would have been shot by the Germans (and their clothes & possessions would have been sent back to Germany for use by Germans). (google Dr Franz Six, the Einsatzgruppe, & Operation SeaLion, then you will know what the plans were & how narrowly we avoided that fate).
I dislike the (WW2-era) U.S.A. government because they did not defend Britain, & they could have saved many more Jews than their quotas allowed. As could Britain (but we did more for the Jews pre-war than the U.S.).
I'm not DM-style obsessed with 'the war' & Germany - WW2 was in another time, & to be blunt - the Channel Island (the only part of the British Isles to be invaded) has a shameful past regarding the Jews during the Nazi Occupation. The local Police collaborated in rounding up Jews. The British administrators of the Islands handed over details of local Jews.
Worst of all? C of E congregations shunned members of their church who were literally only QUARTER Jewish - that rarely happened even in Germany.
I have no illusions about how many British people would have collaborated, just as many thousands of French, Dutch, Belgians, Baltic peoples, Ukrainians, even Poles etc etc etc collaborated & happily joined in with the atrocities against Jews & others.
My basic point is that Nazism did not just expose the 'bad' side of many Germans - it exposed the 'bad' side in many people of all races & nationalities.
We can learn from those times (& sadly, from many other conflicts since then) not to be complacent about our own human character & about what we are capable of - whoever we are.
The DM likes to paint 'the Germans' as the 'potential enemy' still because it's easier to face an 'outside enemy' than to face the truth that we all have inside us the potential to behave as the Nazis did.