Main argument according to reviews is the gap between aspiration and achievement that occurs when engineers' expectations of success are not met is what drives many of us, apparently, to join extremist groups.
The explanatory and predictive power of, "just sore losers" seems weak.
A review of the book (FT, paywalled) summarized other arguments about polarized, binary thinking, and an inability to accept culture, ambiguity, and a lot of what I see as sanctimonious bullshit the way non-STEM students do.
Defense of any principles (right, left, or religious) is considered extremist and dangerously reactionary these days.
One would hope that before laying the critical foundations to discredit educated conservatives (who largely take STEM degrees), academia might dedicate some thought to resolving why there are people with debt-funded $100k+ graduate degrees who read horoscopes, Piketty, and can't calculate a tip.