The "psychopath" theory critique
Now I'm not saying that psychopath theory is necessarily wrong or inaccurate. Nor am I saying people cannot dislike this movie. But I think it might behoove us to consider the problems inherent within that theory when applied this type of comedy.
Ferris Bueller is a farce, which by definition employs exaggerated caricatures and implausible situations to humorous affect. Therefore, the audience is supposed to go in with the understanding these situations will not and cannot happen in reality. Comedy, by its very nature requires the audience members to suspend their disbelief, at least to an extent.
I believe at it's core, that this movie is really about representation, symbolism and wish fulfillment. This movie is made for the teenager, and as such is a glimpse into the teen psyche and a very accurate one at that. The characters and situations are grandiose in order to relate to its audience in a digestible way.
The characters are representations of those wishes and desires. Ferris represents the cool or in control teen, Cameron the coy unassertive uptigtht friend, Sloane the sexy girlfriend, Jeanine the insecure, annoying sister, Rooney the authoritarian tyrant.
Ferris is cool and popular because he just is. Yes, he is manipulative and spoiled and does things that in real life would get him arrested or worse, but recall he is not supposed to be real. He's a human manifestation of teen desire. He has doting parents, a hot girlfriend and can get by on his wits and charm. He never learns a thing precisely because he is the ideal. It is in fact Cameron who learns the real lesson.
Cameron is probably the true hero of the film by virtue of being the least eccentric. His home life is characterized by parents who we never see. He has a father who is at best a narcissist and at worst abusive. It is in fact he who holds all the power in his relationship with Ferris. Consider for a moment that Cameron is the character with a car. Cameron could have chosen not to help Ferris, which have resulted in Ferris not taking in Cameron's dad's Ferrari, which would not have led to it being stolen, and Cameron would not have destroyed it. He in fact states that he knew he could have stopped Ferris all along.
Jeanie and Rooney could also have stopped Ferris. Rooney could have arrived in time to talk to Ferris with Jeannie which would have put yet another snag in his plan. In fact the reason that both Rooney and Jeannie fail is largely due to their character flaws. Rooney's general witlessness and obsession with catching Ferris cause him to break into the house and cause him to be chased by the dog and Jeannie to mistake him for a burgler. Jeannie eventually realizes not to worry about herself but not before leaving school, and getting arrested.
While this movie is somewhat anti-authority, remember that it is written from a teenage perspective and as such is not anti-authority per se. It is anti-totalitaianism. Rooney is disliked not simply because he is in a position of power, but because of his obsession in catching Ferris. He is also completely and totally inept. He in fact could have gone to Ferris' house and found him there. It is also hinted that Grace gets along much better with students,while Rooney does not, perhaps because of his total disdain for the teenage experience.
While the "psychopath" therory is interesting and perhaps even accurate, it is also superficial. While it is true that on a surface level Ferris' behavior is psychopathic, recall that he is is a caricature. His psychopathic nature is simply exaggerated teen selfishness. Every teen is selfish on some level. We all were. This film is not to be taken seriously. Why might this theory be attractive? It could be a symptom of the clickbait journalism culture we live in. Substantive analysis is being replaced by snappy headlines (though I do not pretend that what I have written is anything other than worthless opinion). Another reason may be that millenials cannot relate to the movie the way that previous generations have. We were told by baby boomers that if we simply got that degree we would be set for life. What we got instead was the aftermath of unabashed capitalsm and greed. Therefore, this movie's emphasis on excess and recklessness may rub some the wrong way. However, Ferris Bueller is supposed to be a snapshot into the mind of a teenager, a phase that we eventually grow out of. The film in fact only encapsulates one day. It is therefore perhaps only one event highlighting only one aspect of the lives of these characters, which is why no sequals were ultimately made.
In closing, the "psychopath theory" ,while interesting, is flawed when considering the nature of farce and the total implausibility of the situations. The characters, while relateable, are only so to highlight the absurdity of the situations. Therefore, while on a surface level, this theory may be accurate, it really cannot be applied to a film such as this.