(Sandbox page)
Since we are not being told which accusations made by Grabowski and Klein (G&K) will be taken seriously, I will choose a few at random and demonstrate how they fare when subject to analysis. Having studied many of G&K's claims, I believe these examples are representative. My bolding throughout.
Some statements hint that Jews are racially different from ethnic Poles ... Take the claim in the History of the Jews in Poland article, that Jews have 'specific physical characteristics.' The citation for this sentence is a broken link to a website referencing Nechama Tec. [1] Nechama Tec has said that the Germans used ‘the emotional argument that the Jews of Europe were not simply another ethnic minority, but rather a separate race, with separate and readily distinguishable values and, in particular, physical characteristics.’ Tec never said that Jews looked different, though. Indeed, she emphasized that ‘belying this myth was the fact that the Germans occupying Poland could not, by employing their own distinctions, separate Jew from Christian. [2] There were many stereotypes that Jews in hiding had to be aware of, but it is one thing to be aware of existing stereotypes and quite another to confirm their credibility, as the article seems to do." (G&K, p14)
Looking at the website we find it is a list of difficulties Polish Jews faced in hiding among gentiles, cited to Tec's book. [2] (Tec survived the Holocaust by posing as a Christian.) The relevant item is:
Let's first dispose of the behavioral accusation. The history started when Jacurek copy-pasted the whole sentence from the website. [1] Moonriddengirl later flagged it as a copyvio, to which Piotrus responded by paraphrasing "physical characteristics of curly black hair, dark eyes, dark complexion, a long nose, were in special jeopardy" as "specific physical characteristics were particularly vulnerable". That's it, the whole story. Not only was Piotrus just performing a simple policy-demanded clean-up, he was actually removing the details of the stereotype. Moreover, both before and after the edit the sentence clearly does not say that Jews have particular physical characteristics, but only that Jews with those characteristics were in special danger.
But I'm not finished with G&K yet. Here is the passage in Tec's book that the website sentence comes from; you decide why they didn't cite it:
This is not a great match to G&K's claim that "Tec never said that Jews looked different". But instead they quoted a different passage that appears to support them. But does it? Let's look at the text immediately following the part they quoted:
In other words, Tec is just saying that many Jews could be identified by Poles but not by Germans. So that doesn't support G&K's claim that "Tec never said that Jews looked different" either.
In summary, G&K made a false accusation without evidence and supported it by misrepresenting their source.
References
On page 8 of G&K's essay there is a summary of their overall thesis. I'll quote the part I want to comment on:
Four distortions dominate Wikipedia’s coverage of Polish–Jewish wartime history: ... antisemitic tropes insinuating that ... money-hungry Jews controlled or still control Poland".
"Money-hungry Jews controlled or still control Poland" is indeed a classical antisemitic trope, and it would be a disgrace if Wikipedia promoted it. So we should look at G&K's evidence. However, G&K provide no example of this trope appearing in Wikipedia. I have been unable to locate one either.
Since the trope as a whole does not appear, we can look for the individual parts and ignore the question of whether it is valid to combine them.
Equally problematic in the same article is the sentence, ‘In many areas of the country, the majority of retail businesses were owned by Jews, who were sometimes among the wealthiest members of their communities.’ Since research on interwar Polish Jewry has shown that most Jews lived in poverty, this emphasis on Jewish wealth misleads readers. [1] The citation to this claim is page 84 in a book by one Peter Stachura, but that page contains no such information. [2] In its original version, inserted in 2008, the sentence had no citation whatsoever and was even more misleading: ‘some Jews were amongst the wealthiest citizens in Poland'." (pp14–15)