Perhaps the author knows something about certain topics, e.g., literary criticism, English literature (based on his biography). But in anything other than Western literature (and possibly Western philosophy), it is very apparent that he knows little of psychology, cognitive science, sociology, economics, international relations, geopolitics, history, and non-Western topics generally, to name a few. Yet the coverage of his book touches on these topics, and he bases his opinions on assumptions and biases due to (clearly) having little understanding of these topics.
Most annoyingly, he writes like one who believes himself an intellectual and moral superior. He seems to relish pointing out the flaws in others' writings (giving the pessimists more of a pass), pointing out how optimists looked at things with rose-tinted lenses and barely mentioning "the bad".
Did it occur to him that those authors may not have wanted to detract from the main point and risk becoming unfocused? The type of people who'd be reading those "optimism" books are not children, but people who already are aware of the less-rosier sides of life. And because gosh, it's just SO very hard to find books and articles on social and cultural issues, and the full spectrum of horrible things people have done to one another.
It is unsurprising his worldview is narrow; when one already believes they hold all the answers, they tend to stop looking further, and have a tendency to live in the past. It's like he's still living in an Anglo-Saxon country of the 1950s-1970s (the book was published in 2015), just updated to the modern moral codes that are currently in fashion, with some occasional current events thrown in to seem like he's informed. (Found out later, yes, he was born in the 1940s in the UK, raised, educated, and taught in the UK)
As a result of his biases, there was a lot of conjecture. Much of what was stated are rather based on the author's personal impressions. Though I agreed with a few points of his (after all, even a broken clock is right twice a day), his statements tended to be overgeneralizations devoid of nuance and not entirely accurate, applying a bizarre mixture of news headlines, old English literature, and Western philosophy.
And for not even a 200 page book, how is it that there are so many irrelevant digressions?
In sum, the author is full of opinions on topics he knows as much as the average person in the mid-20th century (but apparently quite unaware of how little he knows), outdated in much of his worldviews (circa mid-20th century), limited in his worldview (possessing distinctly U.K. biases, i.e., American biases are different), and smugly critical of others who have differing opinions or perspectives. Very distasteful.