And consider this A man whose height is seven feet is considered tall by everyone. Reducing the height of a man considered tall by consensus may change the consensus or not. A man whose height is four feet is considered tall by very few people. I believe that the usefulness of language is the consensus we share on the definitions of terms. Precise terms have a mechanism by which we can persuade someone that a specific application of the term is valid.
Vague terms have no such mechanism.
If a person insists on calling a seven foot man short, we might suspect that he is using NBA centers as his reference set, but we would hardly accuse him of a logic error. Vague terms are useful to the extent that we have consensus. When we use them out of context, we confuse each other. It is a fallacy to treat a vague term as if everyone agreed with its definition. We may agree in its application to some but not all members of the universe of discourse.