I think the teacher problem stems from different experiences at school. Everyone of us had at least one abomination of a teacher who was useless at teaching us, and possibly took against us personally for some undefinable reason. Only some of us had an inspiring teacher who overcame that negative image.
If I had only come across the ones who did me down (one even had me creating sick days because I couldn't stand her - and I didn't realise it was because I was sensing what she felt about me), and not the ones who supported me, I too would have had a negative attitude. And I wouldn't have joined the profession, and wouldn't come across the occasional ex-pupil or parent who remembers me with kindness. (I am worried about the lad who claims that I am the reason he joined the profession himself, though.)
It is very sad that there are so many who did only come across the bad apples. and more so that they see fit to slag off all of us as their inferiors.

And, by the way, it can help not to be able to do certain things in order to teach them. You have to analyse what the problems are and thus are able to communicate to the children how to overcome them. I had maths teachers who were brilliant at their subject but absolutely useless and dealing with people with a blind spot. And I still don't know how to distinguish different minerals by their reflectance when seen down the microscope, because the tutor could only explain that things just were what they were. He could tell at a glance, but could not put into words what he was seeing.

And those who can't teach teachers, inspect.