Teacher as Rhetor

For the past few years I've been thinking a lot about the relationship between rhetoric and teaching. This was after seeing a presentation by Gary Woodward on what he calls the Rhetorical Personality. Woodward's ideas about rhetorical personality are from the more modern idea of rhetoric -- or the oldest Sophists -- depending on your perspective. He notes people like Bill Clinton and others who seemed to be able to capture a room and face opposition with poise. I immediately began thinking about how this relates to teaching. Teachers must sometime present things that are unpopular, content they don't know as well as they wish they did, to students who may love them, hate them, resent them, fear them, need them, etc.
Teachers can never have just one self. In fact, no one can. We are all multiples of ourselves. I can't help thinking of that old Michael Keaton movie -- Muliplicity -- where each time he made a copy of himself they became more and more demented in some way. However, they were all legitimately part of him even if those around him weren't aware of all of his selves. Isn't that what we all are? Multiples?! For some people their professions make this multiplicity more or less salient. In teaching it is strongly salient.
There is an idealized teacher -- one that loves learning, is a content expert, is pedagogically neutral, nuturing to his or her students, supportive of a diverse range of students in terms of ethnicity, SES, ability, etc.. But, even if there is such a teacher out there, that is only part of who they are. They may also be [just like Michael Keaton's character] insensitive, developmentally disabled, overly emotional, and a myriad of other things.
There is a need for realization that we are a reflection of our context. Our selves are local and ever changing. In any moment teachers must do the right thing. But, how the hell are they to know what the right thing is? They can plan for a theoretical right thing but in the moment, depending on the student, depending what happened a moment before, what is happening in that exact moment ---- everything can change, the right thing can change. And, you don't know whether it was the right thing until after.
For instance, a teacher puts students in groups because the right thing is to encourage cooperative learning. On Monday it works brilliantly. On Tuesday, a few students argue and the activity unravels and objectives aren't met. The right thing becomes the wrong thing. How can a teacher ever know what is the right thing? Must they know? Or, is it a personality that accepts multiple truths, is flexible, accepting of what the moment brings, the one that is ultimately most successful?