Plato says:

Rhetoric, it seems, is a producer of persuasion for belief, not for instruction in the matter of right and wrong … And so the rhetorician’s business is not to instruct a law court or a public meeting in matters of right and wrong, but only to make them believe.
Then the case is the same in all the other arts for the orator and his rhetoric; there is no need to know the truth of the actual matters, but one merely needs to have discovered some device of persuasion which will make one appear to those who do not know to know better than those who know.

How true, how true… The whole point of any public speaking, be it on TV or in a meeting room, is not to bring the enlightenment but merely to convince. And this simple truth takes years to discover. Some may think that reading Plato in the young age may spare us some difficulty and suffering but I disagree. One must become ready through experience to accept such simple truths.

The obvious consequence should not escape our attention: any public speaking should be seen as an attempt to convince you, not to make you better off. Simple, neh?