It certainly appears, on the face, with regard to the incident that started this thread, that offloading an exit row passenger who refuses to answer the crew's questions about preparedness to assist, is a good call.
But that's no longer really what this thread is about.
There are people who, for one reason or another, are dispositionally unsuited to be placed in a position of authority.
The best police departments, understanding the degree to which their officers have the ability to ruin your day (for example, by fatally shooting you), and understanding the importance of good relations with the community they serve, put a lot of effort into psychological screening and supervision, to weed out those who, given any measure of authority, tend to abuse it.
Other organizations, perhaps less well funded or with less astute management, don't do as careful a job of screening or supervision. And so it turns out that jobs that confer low level authority over others, unfortunately, tend to attract people who gain an unhealthy pleasure from exercising that authority. Think "Shopping mall security guard," or "Middle school assistant principal." Which is not in any way to say that shopping mall security guards or middle school assistant principals are universally psychologically damaged or bad people, but, rather, that bullies are drawn to those jobs.
Every single one of us has seen air crew who fit this profile. I'm not suggesting in the slightest that this was the case here, but I think the matter deserves a little more thought than it's being given here.