We've had a few posters over the years whom I could honestly see in this sort of position. These folks have gotten bent out of shape when things haven't gone their way and have threatened lawsuits and made other unreasonable demands. Obviously with those posters, and with the person in the article, we don't have all the information, but it certainly does make you wonder.
As for general unhappiness about a grade, I can see that being a big potential problem. It's something I myself have worried about a little bit over the years. Recently a parent went to the office and complained about a B that his child earned in my class for the first semester. Although the student earned low As both quarters, the student earned a mid-C on the final exam. Per admin, that final exam counts for 20% of the student's final grade, so the final grade worked out to a B. I understand that the parent wants the child to have straight As, but I feel like the problem with the B in my class isn't really my problem--it's the student's problem. If the student earned As on both quarters, then the student should have earned a decent grade on the final...especially since most of my final exam questions come from (are heavily based on) questions from previous exams. From what I could tell, the student just dropped the ball on the final exam, probably feeling overconfident or thinking that studying wasn't necessary. In any case, the counseling office asked me what I'd be willing to do for the student. I told them that the only thing would be for the student to retake a portion of the exam, but I would only allow that with admin approval (because I think it seems shady to allow one student to retake a final exam because the parent is whiny). I could definitely see parents like this bringing the issue to the court system if they were dissatisfied with the response from the teacher. It's scary.
Caesar, those type of complaints over grades are pathetic on parents and students parts. I once had a serious complaint over a grade I was receiving in a science class in high school. The ironic part of it was that this particular teacher required us to record to the detail our entire grades in the class and keep track of where we were. I did that, and what I had down was not what the teacher had. He disagreed with me, I had proof he was wrong, he didn't like that I was calling him out on it. I can still remember it to this day. I hated science, still do, but was a top notch math student. He was well known as the "hippy science teacher." Eventually he gave in and adjusted my grade, but he did hold it against me the rest of the semester. He really didn't like that I was smarter than him.
There are definitely times where a teacher has made a mistake with a grade. If my own grade were messed up, I would do what it takes to correct that error. I like to think that I am smart enough to recognize that there is an appropriate procedure and chain of command and that it's not appropriate to make unreasonable demands, go over heads, or threaten lawsuits when I haven't gone through the proper channels first.