Max, there is no way you can prove or, for that matter, disprove it. This is a term that does not have a defined empirical meaning.
That, BTW, reminds me of the novel _The Joke_ by the renowned Czech writer Milan Kundera - in which the protagonist sends a postcard with a joke to his girlfriend, the postacrd is intercepted by Party apparatchiks, and the protaginist is accused of Trotskyist heresy. As in all heresy trials, there is nothing he can say or do to prove his innocence - the accusation is true by definition. The protagonist is found guilty by definition and expelled from the Parnassus. An interesting book to read nowadays, despite its sexist overtones.
Wojtek