There was, if my understanding is correct, a large difference between the rank-and-file and officer corps of the Germany army, and the more political SS/SD personnel. Indeed, the former tended to have older aristocratic connections and didn't particularly care for the party.
Had the author made that distinction it would've been helpful, or had they perhaps instead used some of the Japanese or Soviet forces as an example it would've been better.
The thing with the German army ("Wehrmacht") is that for decades Germans told themselves that sure, SA/SS were evil and did horrible things, but the Wehrmacht was "clean", so granddaddy never did anything wrong, he was only defending his country.
Then in the nineties, https://en.m.wikipedia.org/wiki/Wehrmachtsausstellung came along, showing how the common Wehrmacht committed its share of atrocities.
When I went there with school I actually had my grandmother calling me on the phone, in tears, telling me that her husband was no murderer.
This exhibition ripped apart a few lies we Germans had told ourselves about our honorable Wehrmacht.
But even for these forces, I think the claim that they are all to be regarded as evil goes too far. Were there individual evil Japanese, Soviet, and German soldiers? To be sure—but there were also evil American ones. More importantly, does serving an evil government make you evil? Since 'evil' is determined, as history is written, by the winners, this would seem to amount to the claim that being honourable largely amounts to picking the winning side in advance. (I think positing instead an absolute definition of 'evil', as a disagree-r may be tempted initially to do, is probably untenable.)
This seems to be a key idea in his argument, given that it is, as he says, the "simplest, most extreme case". However, I'm not so sure that this is true. Do most people view Nazi soldiers—that is, boots-on-the-ground troops, not leaders—as evil? I've always understood the historical consensus, to which I am sympathetic, to be that they were subject to a misguided ideology, but not evil.
Further, even this assumes that people are willingly fighting for the country in whose military they serve. This was not at all true in Germany, and has failed to be true in the US, as well. In fact, arguably, even when no-one has been drafted, many people have joined in the military under the assumption that they will never serve—in some cases, a factual error, but surely not one to which honour or dishonour can attach. Two non-rhetorical questions: is it dishonourable to serve in the military only to avoid legal repercussions? What about more severe repercussions—say, bodily harm? What if those repercussions are to be visited on others—say, one's family?