Read "pretty tale" as "illusion," and give the dialogue universal scope, and it takes on a sinister and profound double meaning. I.e., the most "dangerous man" is the cynic who fastens the dream-ideal upon mankind with full understanding of its destructive nature. It is an act worthy of "the devil himself," the parallel between that personage and Monygham being vivdly suggested by the timing of Monygham's interruption, as if responding to the sound of his own name. Further comparisons between Monygham and the devil are to come.