dustin smith , a 21-year-old gay man in bismarck , received messages and explicit photos from user going by top man ! on grindr .
smith realized that user was staunch state conservative randy boehning after reading of the lawmaker 's vote against a gay rights bill this month .
smith went to the press and boehning soon admitted he uses the gay app -- but the 52-year-old says its part of a rival 's smear campaign .