It's a rant people. By definition, it doesn't pretend to be nuanced and to account for the positives, and it usually comes out of temporary frustration or anger.
Profs and TAs have their own collective blog devoted to bitching about their students: http://rateyourstudents.blogspot.com/
Indeed. And that's why there's an entire section of CL devoted to people ranting about the annoyances of their daily life. Not all those people are bitter, angry, arrogant assholes.There are lots of jobs that include among the job requirements faking a certain level of intimacy. Most of them, of course, require only a very shallow level of fake intimacy, and don't have it as the main requirement of the job, but there does seem to be a pattern of people in such jobs bitching about the customers. Professors bitch all the time about the students we're suppose to act like we care about (not that we don't really care about any of them, but it's part of the job to pretend we care about them all equally, and it can be very stressful and frustrating keeping that up with the really annoying ones). It may be that all we should conclude here is that in a job which makes a much higher level of fake intimacy basically the core of the job description, the level of bitching about customers can rise in proportion.
Profs and TAs have their own collective blog devoted to bitching about their students: http://rateyourstudents.blogspot.com/