Helps you identify various dangerous people and deal with them - not by colloquial myths of allegedly dangerous behavior, but by real-world systems of classifying & filtering information to understand what is & will happen. Author is regularly hired to deal with crazies threatening anyone from us peons to presidents.
Back when I was taking some late-in-life college courses, the prof was discussing a "disgusting" book. Forgot the name, but it detailed how to screw everybody so you can get to the top. He spent a good 15 minutes vilifying the author and the subject.
Stopping to catch his breath, he asked for a show of hands of those who would read it. Mine was the only one that went up. The rest of the class looked at me in horror or revulsion.
He said (with a superior smirk) that evidently I agreed with the tactics (and was therefore a Bad Person), otherwise why in the world would I read such a book.
I explained that I could then recognize the tactics some back-stabber would use in trying to get ahead of me, and take appropriate counter-measures.
There was a "Look, there's Elvis!" moment as we moved on to something else. After class a couple of classmates came over and said that they never thought of that.