Even Nazi historians wrote about Polonization of Germans throughout ages.
Of course they perceived that Polonization as something bad ("cultural degradation"), and advocated for Re-Germanization of "racially suitable elements".
An example of such a Nazi historian is Kurt Lück - who in 1934 published a book in which he wanted to prove that almost entire Poland was once inhabited by Germans (both towns and villages), but they were later Polonized by "evil Polish nobility". In one of his maps, Kurt Lück showed German settlement in Southern Poland (from the eastern border of Upper Silesia to Volhynia and Podolia), and he marked there villages and cities with Medieval German immigrants. He also painted a huge territory with yellow colour as "Verbreitungsgebiet" ("range of distribution") of Germans , which covered nearly entire region - from the easter border of Upper Silesia in the west to areas around Lviv in the east.
In that map Kurt Lück marked 123 cities and divided them to 5 groups (I called them A, B, C, D, E below), depending on when inhabitants of each city were Polonized:
Which translates:
A. Among the numerous names of citizens attested by documents until
1500 over 90% Germans. Polonization not until the 16th century and later.
B. Overwhelming predominance of German names until 1450. Beginning of
Polonization 1450, completed in the first half of the 16th century.
C. Few citizen names, the majority German though until 1400.
Polonization mostly completed in 1450.
D. Name material does offer few insight or not existent at all, or
assembled respectively. However, all criteria allow the conclusion
that Germans played an important role during one century in the towns
that formed in the 13th century, and only in the first decades of the
places endowed in the 14th century.
E. The research results until now do not allow inferences about the
presence of German settlers.
Group "E" according to Kurt Lück, numbered just 11 cities (out of 123). In his map he also marked hundreds of villages in Southern Poland where Germans settled.
Still Kurt Lück was among those "better" Nazis, who advocated the Re-Germanization of Poles, rather than the extermination of this nation.
The reason why Kurt Lück advocated for Germanization and assimilation of conquered Poles, was his belief that many if not most of Poles were descendants of German Ostsiedlung immigrants, who settled in Poland during the Middle Ages and were later Polonized - "culturally humiliated" - by Polish nobles during the 1400s and the 1500s.
Kurt Lück thus considered the Polish people as "Aryans", but "depraved and demoralized Aryans". He also believed that some Poles had "strong admixture of Jewish or Russian subhuman blood" - and those were to be annihilated. Here is what German wikipedia today writes about this Nazi historian:
In seiner wissenschaftlichen Arbeit verband Lück geschichtswissenschaftliche und volkskundliche Aspekte mit einer aktiven Feldforschung. Polnische Arbeiten bezog er in seine Studien mit ein, nicht ohne jedoch jederzeit die kulturelle deutsche Hegemonie zu betonen. Der Materialreichtum der Werke macht sie zweifellos bis zum heutigen Tage als Quellensammlung nützlich, allerdings muss der völkisch-nationale Ansatz immer mitbedacht werden.
Which translates:
In his scientific work, Lück combined historical and ethnographical aspects with an active field research. He involved Polish works in his studies - however, not without constantly emphasizing German cultural hegemony. The richness in material of his works makes them useful without doubt until today as a collection of sources; however, the folkish-national approach has always to be kept in mind.
As you can see Kurt Lück did not consider Poles, many of whom had "German blood", as racially inferior - he considered them to be culturally inferior.
The Nazis also believed, that Poles had a strong admixture of "Jewish and Russian blood", which made some of them - but not all - racially inferior.
As for Kurt Lück - he devoted his entire life to fight against Polishness and Poland as a state.
In 1918 - 1919 he fought against Polish insurgents in Posener Aufstand as a German Freiwilliger, including the defence of Kolmar on 08.01.1919.
In 1922 he founded "Verein Deutscher Hochschüler" in Poland. After 1934 he was an important member of German minority in Greater Poland - chief of "Historischen Gesellschaft für Posen" and editor of "Deutschen Monatshefte in Polen" and member of "Nordostdeutschen Forschungsgemeinschaft".
He was arrested by Polish authorities before the war started in August 1939, but soon he was released. Then he volunteered to Volksdeutschen Selbstschutzes, which participated in persecutions of Polish population in occupied territories.
Then he became director of Gräberzentrale für die ermordeten Volksdeutschen, which was researching "Bromberger Blutsonntag" and similar cases.
In March 1940 he joined the SS (in rank of a captain) and in the Autumn of 1941 he joined the NSDAP (but he joined retrospectively - since December 1940). He participated in the action of repatriations of Germans from Eastern Europe into western parts of Poland annexed directly into the Reich in 1939.
After the outbreak of German-Soviet war in 1941 he volunteered to the Wehrmacht on the Eastern Front
(sic! - volunteered to the Eastern Front! - what a fanatic!).
In March 1942 he was killed by Soviet partisans.