In his English translation of Chelmno [here], Mattogno tries to defuse Höppner's memos of 16.7.41 and 3.9.41. He systematically distorts Aly's summary of the memos, which appears in Endlösung [here]. Below I contrast Aly's account (from the English version of the book) with Mattogno's distortion.
Five features of Höppner's position must be stressed. Firstly, he was based in Posen, the same SS apparatus that contained SK Lange. When Höppner asked "whether
the most humane solution is not to finish off the Jews who are unable to work by means of a quickly working agent" (see here), he would surely have had a broad idea of the 'agent' concerned, namely poison gas. Secondly, Höppner recommended that all female Jews incapable of work be sterilized, so there is no doubt that he favoured the total genocide of unfit Warthegau Jews within "this generation." Thirdly, as Evans notes here, Höppner's language was echoed in Hitler's last testament. It also reappeared in Wetzel's draft to Lohse (NO-365) and in the gassing rumor noted by von Payr on 8.8.41 following the first Libau massacre (Aly, pp.217-218).
Fourthly, and crucially, although Höppner anticipates deportation to the Soviet interior, he makes it clear that this cannot happen until "After the end of the war..." This point is stressed by Aly (p. 221), who also notes that Höppner was aware of how "time-consuming and hopeless plans for mass deportation can be." Fifthly, he emphasizes that "it would be pure fantasy to discuss further organization of these intake areas [in the USSR]" until a decision had been made as to whether the Jews would be "totally eradicated" (see Browning, p.6, here). This clearly implies that Höppner was pushing for a killing decision (a Hitler "green light") rather than musing about resettlement, which he knew was becoming unlikely as the end of the war stretched farther away.
How does Mattogno handle these documents, which clearly blow away his resettlement fantasies? Although Mattogno acknowledges that Spring 1941 resettlement plans were meant to be implemented "after victory" (p.24), he blithely ignores the significance of this fact for policy-making in the Fall, when hopes of quick victory were being dashed. Mattogno then quotes irrelevant journal articles on the Pripet marshes to mislead the reader into thinking that Pripet was still a serious proposal in Summer 1942 rather than Summer 1941. He ignores Aly's citation of Hitler's dismissal of the project in September 1941 (see footnote 346 here for Aly's source). Mattogno then simply states that the Höppner memos are "not consistent with a plan for systematic extermination", but this ignores the fact that Höppner was referring to partial extermination, namely on unfit Jews. Mattogno simply obscures what Höppner actually says by focusing on what he didn't say ("total extermination"), even though this is irrelevant to the historiography of that timeframe.
Mattogno's view that Höppner's memos are harmless is not shared by some denier colleagues. Weckert implied here that the 16.7.41 memo is a forgery. Perhaps if Mattogno had done the same, he would not have needed to misrepresent both Höppner and Aly so crudely?