We are all teachers.
No matter which way you look at it, we have all taught others a little bit about something we know. Sometimes we are good at it. Some go into it as a career.
[And at this point I need to cool down, lest I say something that will bring the pitchforks and torches against me]
But I will somehow get my word out, and the bottom line is this: there are some businessmen who should not be businessmen. There are some doctors who should not be doctors.
And there are some teachers who should not be teachers.