The PHB has decided on a course of action based on some prevailing prejudice current when s/he made the decision. Because the PHB is not sufficiently secure to change course, every peice of evidence presented after the course is set must be rejected. Often the PHB will admit the evidence is significant by asking that it not be presented - since the course has already been set, listening to it would be a distraction.

This method greatly simplifies the PHB's life, because contradictory evidence need not be considered at all, and supporting evidence is just "feel good" stuff.