I don’t think its wired to critique someone for having a widely different interpretation of what happened than multiple others that were directly involved and then taking this very peculiar subjective interpretation to make wide sweeping (and IMHO wrong) conclusions about what we should learn from it.
It is because that's literally what the book is about. The book is addressing that very phenomenon as its core thesis. That's exactly what he is talking about when he says that the protests are illegible. If someone says "people disagree a lot about what happened and that's a problem" responding to that by saying "i disagree about what happened" isn't really engaging with the argument.
My impression is that Bevin started out with a preconsived notion and then kinda made up a retrospective narrative of these protests to fit to that.
I'm sorry but I don't think that anyone who has actually read the book in good faith can come to that conclusion.