“As Jim [Spahr, Office of Naval Intelligence] learned his job better, he was astounded at the variety of intelligence gathered on homosexuals by the police and government. The FBI followed people to gay bars, checked license numbers of cars parked outside, and followed people home to see with whom they had made an assignation. The San Francisco police, like police in may other cities, freely shared with the FBI and military police files of men and women they arrested in raids on gay bars, so that everyone had up-to-date lists of deviates.”
Conduct Unbecoming: Gays & Lesbians in the U.S. Military by Randy Shilts, page 51.
See this quote for more information on Jim Spahr’s job with the Office of Naval Intelligence.
no kids, no wives, dead to their families; can’t be threatened: dangerous
Actually, a central point of the military’s argument was that gay service members would be vulnerable to blackmail by enemy agents/military. In other words they believed that they very much could be threatened as most were not out to family and friends. They stood to lose those relationships, and if outed as gay, it would also affect their job prospects in the civilian world. Especially if they were discharged from the military because of it.