1) a teacher can accuse a parent of "cyberbullying" for an email sent in purported confidentiality to others, and that the claim can be taken seriously. Obviously I didn't read the email, but the author seems well-read and reasonable, so I'm inclined to conjecture that whatever he sent wasn't outrageous. If I as a parent were "called in to the vice principal's office" and accused of cyberbullying a teacher, I'd laugh in their face. Is this teacher teaching middle school, or in middle school?
2) that the parent is having constant meetings with school officials, and seemingly-frequent interaction with other parents via email. Granted in my days (mid-90's or so) email wasn't a big thing, but my parents typically took the hands-off stand of "did the teacher say so? then do it", plus the occasional PTA meeting. (They did help when asked, but I can probably count all the face-to-face meetings they had with school faculty on one hand). And that's a stance I can very much appreciate. I don't know what parent-teacher relationships are like today, but it sure sounds like the teachers are hearing almost as much from the parents as they are from the students.
Which isn't to say the system can't be improved. But honestly I remember nearly as much homework from my days, and those points stuck out more to me as a sign of the times.