MM is rarely explicitly racist; it's more like he espouses ideas that obviously entail racial superiority and then stops shy and pretends like you're an idiot if you actually believe those "obvious" entailments The Progressives or whoever have been selling you.
(Preface: It's hard to explain, and the following might sound like a bit of an ad hom, but that's not how I mean it. It's just a really useful lense through which to view MM's writing -- especially if you find yourself thinking "he's just saying kinda true things that aren't very PC!". Understanding the rhetorical ploys an author is using can help you see through the trees to the heart of the author's argument and then -- in MM's case -- be sure you're well-founeded in summarily rejecting it.)
Reading MM is like reading an above-average-but-not-exceptionally-bright high schooler who went on a depth-first search of Google for every topic he writes about. The authority emaninating from a depth-first search is obviously flawed because it ignores the forest for the trees, but can be oddly convincing if you don't notice what's going on. Or at least difficult to refute in a clear-headed and logical way because you get stuck in the quagmire of meaningless specificities.
Concretely, MM's writing generally has a well-developed thesis with logical arguments and reasonable citation, but falls flat on its face for reasons that can only be described as "common sense". MM's hope -- or maybe his own blieve -- is that his authoritative knowledge of particularities supporting his point trumps the forest of "common sense" generalities.
But the dozens of obvious objections that aren't addressed by MM -- or are just hand-waved away with a bit of rhetoric about some evil other (progressives, etc.) -- really are at the heart of the matter. A few historical examples really are no replacement for a global view of historical reality.
Of course MM is smart enough to be well-aware of the elephants in the room. However, he's maybe more interested in trolling than in debate. Or maybe really does blieve they're unsubstantiated progressive lies. IDK. In any case, instead of addressing these elephants head on, he kind of summarily dismisses the most obvious rebuttals with a bit of a literary eye roll.
For example, in one comment he rambles on about colonialism being not-so-impeachable because those Africans were brutes prior to and after colonization. The problems with a statement like this really are quite obvious, but his comment goes on at length about particularities of specific European leaders and African dynasties instead of addressing head-on the litany of common-sense high-level objections to his poisition.
It's like when a high schooler puts forth a totally untenable position that is just wrong, and considers himself unimpeached because no one in the room has a response to the particular arcane knowledge he used to backup his point. Even though that knowledge was totally tangential or at best provided one supportive data point in an infinite sea of data suggesting he's dead wrong.
I think people who disagree that MM's writing is racist are mostly just hoodwinked by the above rhetorical ploy -- getting so specific about a few trees that the reader forgets about the forest, and therefore conclusing that the author doesn't need to be held responsible for the obvious historical entailments that follow from his advocacy.