There may be nothing more frustrating in the world than being unable to convince somebody that something is a tautology. You try as hard as you can to convince them that something is true by definition, but they persist in failing to see how you have designed the terms of the statement to be indistinguishable from the conclusion. Saying “Dogs are dogs therefore dogs are dogs” and having someone say, “Ah, but there are many kinds of dogs” is enough to drive one batty, if it happens often enough. Essentially, this is because the supposed point of contention is nothing of the kind – it is just a non sequitur that the other conversant thinks is some kind of rebuttal.
For some reason, training courses seem to spawn these sorts of logically agonizing discussions.