Sometimes a white person says something about people of colour that is untrue, and when you correct her, the white person will insist that she is right because she read it in a book.
You know that it is untrue because you do not (or somebody you know does not) fit into that generalization; thus, it is inaccurate to say that people of colour have that property, without qualifiers. For some reason, the white person believes that the written word should override the lived experiences of people of colour, even when that book is a fictional portrayal of, a study of, or an interpretation of our lived experiences.
Note that to give priority to one’s lived experience over a book in this case is not a case of anti-intellectualism. (However, it is probably often dismissed as anti-intellectualism by the white person, because of the assumption that people of colour are against book learnin’ and are opposed to something because it comes from a book.) Instead, disproving a universal claim by using one counterexample is an application of predicate logic.
To disprove the claim, “All X have property P,” all you need to do is to show, “There exists an X without property P.”