I have a few random thoughts about this, none of them should be taken as the whole story.
It is always sad when people don't like us our our children, especially people in power. I still hate it when I get one of those bosses. But there is always someone, a co-worker or a boss or a person in our social circles, who we do not get or who do not get us. Learning to deal with that can be an important skill. I wouldn't want it to be the primary experience of growing up, but a few teachers here and there, especially with parental support and coaching, might be turned into a useful experience.
There is a teacher at DS's school who was having mini strokes for a year before they got diagnosed. She had been a great teacher until she started to decline. People noticed there was a problem, but it took doctors a while to find out what was really happening. Another teacher has a wife with a chronic illness, another teacher's spouse died just before school started, and another one suffered from 5 months of morning sickness. All were great teachers, but probably not all that great when their lives were so disrupted. I happened to know about these ones, but what other problems might a teacher have that would not become public? Maybe she shouldn't have been teaching, maybe she was never a good teacher, but sometimes there are good teachers who have to just keep working, no matter how hard things because they need the money or the benefits or to make it through to retirement.
I don't want to suggest that it isn't really sad that your son felt this way. It is sad. But I wonder about "the rest of the story...." Maybe seeing it that way could take a litte of the sting out of the pain. Or maybe not....
