Continued -- 
3. Abuse takes many forms. I didn't specify sexual abuse, but statistics show some students not abused are harrassed.  And there is a history of covering up problems and moving those teachers around.  My nephew's 6th grade teacher abused 3 girls & dished out verbal abuse to the boys. He'd been passed off from other districts until he was finally arrested. 

There are teachers who throw kids against the wall, mock, hand out "most likely to be a terrorist" awards, & verbally abuse kids. I'm sure you were a wonderful teacher who never abused students. My kids had teachers who were verbally abusive to them & others in the class.  

4. Removal of teachers - are you not aware that there are teachers in various states who are suspended with pay for YEARS? If they are even removed.

There is a history of these problems, whether you saw them or not.  Are innocent teachers tarred with that brush? Yes. But there is a foundation of facts that contribute to the stereotype described.