Where people have posted about the actions of a teacher, there will often be comments from other teachers responding with balanced points. Occasionally the teacher might be an asshole, more likely a bad moment, often an unreasonable expectation from the child/ parents.
The problem with "teacher bashing" is that it's on so many levels. There is an agenda through the government /OFSTED that then gets fed through the media (Daily Fail and the like) that teachers aren't good enough. Even "satisfactory" which should suggest that the expected standards are being met was removed a few years back, with schools (and until recently) teachers being graded Outstanding, Good, Requires Improvement. The levels of scruitiny have become intolerable and counterproductive with teachers being scapegoated for issues beyond their control. Everything must be accounted for and analysed for back covering which takes time and energy away from the core business of teaching young people. Sadly many senior management teams I have encountered have been less than supportive. Academisation is a back door way of breaking down nationally agreed terms and conditions. Schools rarely offer permanent contracts to new staff, usually one year contracts. There is a constant threat of capability proceedings against anyone struggling with the pressure. For a minimum of 4 years university study, the salary isn't fantastic.
These problems certainly aren't exclusive to teaching. I haven't got substantial experience outside teaching, but the way the government has been dealing with junior doctor contracts is part of the same mentality.
DH is in the private sector doing something utterly different. He works long hours and isn't immune to bringing work home, but at least gets double the pay, and doesn't have the negative culture surrounding his occupation (although it's likely to attract the label of boring 
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What I'm saying is, that it's complicated. Teaching has changed. Some changes bring better outcomes, but there is too much baggage, complexity and rate of change. (Very rarely can a lesson be reused these days because each class has different needs and the curriculum changes constantly.) There is a depressing culture in our society over the last decade of squeezing out more and more on less and less resourcing, and that applies to teachers, the NHS, Sports Direct warehouse operatives etc.
Teaching, like many other occupations is tough. It tends to attract unfair criticism from people that don't see the leg work in the background. There is a minority of assholes, but most do a good job in challenging circumstances and get tired of constant negativity directed at them, particularly as many teachers went into the profession with idealistic values.
I'm not saying it's the hardest job (That's subjective; I couldn't deal with the emotional toll and shifts of policing for example), but by and large, it does deserve respect.