Does the CBS documentary that is a plot element in Masters of Sex (season 2) exist in reality?

There are two possible events they may be referencing in the show. The first is from the show ABC Stage 67 which ran on the ABC network in the United States during the 1966-67 television season. In a documentary episode entitled Sex in the Sixties which aired January 12, 1967 Masters and Johnson did appear to discuss the changing sexual mores and manners of American society.

The other event the show may be referencing is from a Canadian television show called Here Come the Seventies which ran on CTV from 1970-73. For the March 18, 1971 episode entitled Sex: Breaking Down the Barriers TV Archive Canada gives the following description:

In the '70s the human biological function known as sex will be more researched, more exhibited, and will probably undergo more attitudinal changes than ever before. Featured are interviews with Masters and Johnson, Dr. Martin Shepard, a psychiatrist, a homosexual and a lesbian who explain the reasons for their preference.

Trivia about this episode from Imdb claims

During production for this segment, the Canadian crew traveled to St. Louis to meet and film Masters and Johnson in their own working environment. This may have been the only occasion on which a television crew from an independent production company was allowed to film in Masters' and Johnson's clinic. (Many years later, Virginia Johnson stated that no film crew had ever been granted privileges in their lab.)

Why Masters of Sex would say it was a CBS documentary though is likely due to Showtime and CBS both being under the Viacom umbrella at one point