Before Stonewall is a unique piece because it was made in 1984, 15 years after Stonewall: It was still fresh in people's memory, it wasn't so long before.
Above all, it means that the people interviewed in the program were old enough to remember what the 20-30s were like, remember an experience in the army during the Second World War, remember life as a young gay person in the fifties. Most of those people wouldn't be able to be interviewed today: Most probably died of old age and many probably died of the greatest tragedy to ever affect the gay community a bit after the documentary was made: the aids epidemic.
Thus this documentary is invaluable to anyone interested in gay history, and one can really feel grateful that it was made back then, that someone decided to collect all those memories and amazing life experiences, or they would have been lost for ever.