Violating the Principle of Rational Discussion

On page 202 of Critical Thinking, Epstein illustrates that Violating the Principle of Rational Discussion is pretty much an argument that is intended, or not, to mislead another person. The principle of rational discussion is that we want to try to use all of our reasons for and against a theory, when talking about a theory that is definiteyet able to be criticized. But VIOLATING this principle, refers to an argument that is not entirely true. This fallacy relates to people who sometimes say a premise or premises that are not relevant to the conclusion. This particular person may not have purposely misguided the other person he or she was talking to. However, there are certainly times where a persons intentionally violates the principle of rational discussion.
For example, When I play baseball, there are always guys who talk bad about a Coach. They often say that this Coach is dumb, or doesn't know what he is talking about, or even that he deserves to be fired. But the funny thing is that more times than not, it is the player who is out of line. He will say a Coach is bad only because he can't handle the pressure a Coach puts on him. And he may say a Coach doesn't know what he's talking about; when in reality, the player is just capable of doing particular drills the right way. So this player is actually sending out the wrong message about a Coach being bad, when he really is the "bad" one.