The Gay Deceivers (1969)
The Gay Deceivers is a 1969 gay-themed comedy film with a twist ending. The film derives much of its humor through the use of stereotypes. According to gay film historian Vito Russo in his book The Celluloid Closet, co-star Michael Greer, who played the flamboyantly gay Malcolm and who was himself gay, tried to work with the screenwriter and director to minimize the negativity of the characterization and present Malcolm in a positive light.
More at Wikipedia.