Updated Dec 18
When they have committed a relevant act which I view as legitimately criminal. Especially if there is legitimate public interest and/or hypocrisy.
The case that springs to mind is that of former US Senator Larry “Wide Stance” Craig, who was arrested in 2007 for soliciting sex with an undercover policeman in a public men’s toilet.
First, people have the right to use a public toilet without being sexually propositioned.
Second, Mr. Craig was an elected government official with a history of openly anti-gay attitudes regarding legislation.
A more borderline case is homophobic Christian evangelical pastor Ted Haggard. While I have very little sympathy for him, my hesitation is due to the fact that I don’t believe that drug use and paying prostitutes should be criminalised. Although there was an allegation that some of his actions may have been non-consensual, in which case I would say go ahead and publicly prosecute. Also, while he made himself a public figure with some influence on his audience, he wasn’t an elected government official.
Mr. Haggard’s actions were repulsive in terms of both public hypocrisy and in cheating on his wife. But, again, it seems borderline.
Similarly, it would be acceptable to out someone who had perpetrated sexual harassment, such as in a workplace or educational context.
Another context would relate to the cheating issue. If I knew a heterosexually married woman, and also knew that her husband was going around having sex with random guys in public toilets, I would tell her. It’s not only cheating – it’s dangerous in terms of diseases. Although it isn’t a gay-specific issue, since I would view it the same if the cheating/promiscuity was heterosexual.
Lastly, it would be reasonable to disclose in a medical situation, if the patient were unconscious:
“Doctor/nurse/EMT, I’m Jane, and I’m Diane’s wife, so I can receive medical information, and can contribute to medical decisions.”
“Doctor/nurse/EMT, I’m Sarah, and I’m Sally’s best friend, so I know she takes estrogen, and I also want you to be civilised when you remove her clothes to examine her.”
If it’s your coworker, neighbour, acquaintance, or even someone you think is your friend, and you are just gossiping to get attention and seem like you have something interesting to say, Absolutely Not.
If you fancy yourself as a “social justice warrior”, or an “ally”, or want to do liberal virtue-signalling, Absolutely Not.
If you are LGBTQWhatever, and think everyone should be as out as you, Absolutely Not.
Personal information is a type of personal property. And it is the individual’s personal choice to either share or withhold access. This applies to many other areas besides the ones in the present question.