The patients in the hospital were there for care and supervision; we, the audience, are to assume that for whatever reason they were unable to care for themselves. Part of the role of the head nurse is to maintain order and authority over the patients who as mentioned were unable to care for themselves. That's no more wrong than saying that a teacher has to assert authority over a classroom, a parent has to assert authority over a child, a boss has to assert authority over a group of employees.
The patients were in the hospital because, for one reason or another, they got put there, and there are bars in the windows and locks on the doors preventing them from leaving. And you got nothing from the book or the movie if at the conclusion you missed the point, which was that the people locked up in the psych bin were primarily or solely impaired by the psych bin and its staff. The main character McMurphy opted for psychiatric incarceration under the mistaken belief that it would be better for him than conventional jail/prison. We meet the other characters through his eyes and find some that have been shaken by other people until they rattle and roll pretty badly (Billy) but there doesn't really seem to be anything wrong with their mental equipment; even the most disturbed catatonic space cadet present on the ward, the Big Chief, turns out to be cognizant (as McMurphy suspected).
Why would you take the word of the system that these people were locked up and under the control of the people running the place because "they needed it"??
See my next post on this same thread
The SDMB Posts