In any prosecution under ORS 167.075 and 167.080, it is an affirmative defense for the defendant to prove:
(1) That the defendant was in a parental or guardianship relationship with the minor;
(2) That the defendant was a bona fide school, museum or public library, or was acting in the course of employment as an employee of such organization or of a retail outlet affiliated with and serving the educational purpose of such organization;
(3) That the defendant was charged with furnishing, showing, exhibiting or displaying an item, those portions of which might otherwise be contraband forming merely an incidental part of an otherwise nonoffending whole, and serving some purpose therein other than titillation; or
(4) That the defendant had reasonable cause to believe that the person involved was not a minor.