The excerpt that Michael quoted refers only to Upper Silesia which was an autonomous region, with its own Parliament. The Polish government had no direct influence on internal affairs of Upper Silesia.
Moreover - the excerpt that Michael quoted mentiones the policy of Michal Grazynski (voivode of Upper Silesia) - Grazynski became the voivode of Upper Silesia in 1926 after Pilsudski's Coup d'Etat - because Pilsudski supported his candidacy. Considering that Pilsudski was extremely pro-German, it is hard to believe that he would choose an anti-German person for a voivode - which puts in heavy doubts what Michael's account claims.
Using Michael style of argumentation about "pro" and "anti" things.
Another issue is that the excerpt quoted by Michael describes no any details about that alleged "mistreatment" of Volksdeutsche in Upper Silesia. The only things which this excerpt mentions regarding this issue, are empty slogans - such as "Polonization" or "making life miserable for Volksdeutsche". But it does not say how exactly life was being made miserable for German minority, or how exactly was that alleged "Polonization" conducted.
In fact voivode Grazynski did not carry out any action aimed at depriving the German minority in Upper Silesia of its national culture, language, or any other minority rights, or civil & political rights of Polish citizens.
The only thing which could be interpreted as "Polonization" - but surely in fact was nothing close to "Polonization" - was supporting and actively promoting Polish culture in Upper Silesia - for example by promoting the creation of Polish museums, Polish theatres and various Polish cultural organizations & institutions.
All those actions - however - were not followed by any hostility towards German culture. Although he did not promote German culture - he clearly did not fight against it and did not prevent its development.
So it seems like US Ambassador was clearly "oversensitive" or biased, and he exaggerated the problem.
I don't know what else can be expected for a national minority in a foreign country.
Promoting German culture by a Polish patriot (such as Grazynski)? Please let's be serious. Great Britain somehow doesn't promote Polish culture nowadays, does not build Polish museums and Polish theatres in London - despite the fact that Polish national minority in Great Britain is very significant since Poland joined the EU.
Germany neither does promote Polish culture - or ever was - despite having numerous Polish minority.
By August 1939 that persecution was far worse than it had been in January 1937, when Ambassador Cudahy made his report back to Washington.
An unsupported claim by Michael Mills.
This Embassy has, in a number of despatches, reported the loss of German capital by Polish confiscatory tax methods and the coercive measures
The loss of German capital had of course been the case - but it was the loss of FOREIGN German capital - i.e. capital of businessmen from Germany, not capital of local Polish citizens of German nationality.
Combating "invasion" of foreign capital by establishing more demanding tax methods and coercive measures - was something normal for any country which wanted to promote local, national businesses.
The European Union did not exist at that time, the European Economic Community did not exist too.
which have forced many Germans out of work in Upper Silesia.
Well - but also many Poles who worked in foreign, German factories.
However - I suppose he refers to forcing out of work Germans from eastern regions of Germany who worked in Polish Upper Silesia (as you probably remember majority of factories were in that part of Upper Silesia which was Polish after 1921 - the German part of Upper Silesia, although larger, had fewer factories).
Polish citizens of German nationality had exactly the same prospects of finding work in Upper Silesia, as Polish citizens of Polish or any other nationality - so it was definitely not discrimination of German minority.
It could be "discrimination" of immigrants from Germany who wanted to work in Poland - but this was perfectly justifiable, as no state had any obligation to allow hordes of foreign immigrants to work on its territory.
He claims writing about discrimantion of minority, while in fact he writes about discrimination of German capital - and foreign German capital, to be precise - not capital of Polish citizens of German nationality.
These are completely different things and while discriminating minorities in your country was perceived as something bad also at that time - in early 20th century - then favouring national capital over foreign was certainly not something unusual and not something perceived as bad at that time - there was no EU or EEE in 1937.
During my first month's residence in Poland I was at a shooting party given by the President near Cieszyn with Herr von Moltke the German Ambassador who, in a surprising outburst, told me that the situation in Upper Silesia violated "every principle of justice" and strained his patience to the breaking point. The openly hostile discriminatory tactics of Polish governmental authorities toward German industry and German residents in Upper Silesia have for many years been the cause of much tension between the German and Polish Foreign Offices.
I am not surprised that von Moltke was angry. However, he was so blinded by his anger that he forgot that it was Germany - not Poland - who first started the "economic war" against the Polish state.
It was Germany (already before Hitler came to power - Weimar Germany) who first refused to import Polish coal from Upper Silesia - which forced Poland to export all of its coal via the Baltic Sea.
Thus I don't understand why Germany was later angry that foreign German industry (and of course national German - not Polish industry ran by ethnic German citizens) was treated in a "hostile" way.
Germany started the Polish-German economic war. They got what they wanted.
That economic war was indeed the cause of tensions already during times of Weimar Germany.
There are words which carry the presage of defeat. Defence is such a word. What is the result of an even victorious defence? The next attempt of imposing it to that weaker, defender. The attacker, despite temporary setback, feels the master of situation.