Earlier quoted context omitted.
Infidelity is not a private matter however: the person being cheated on has the right to know. For a million cheaters, there's a million their SOs, often living miserable lives but denied an informed choice about their future and kept at non-negligible health risk. It stops being a private matter when it trespasses into other people's life.
I can see the person cheated on having a right to know. Everybody and his dog? If I know that my neighbor Joe is running around on his wife Jane, I might be justified in telling Jane; stapling fliers announcing to the telephone poles up and down the street seems a different matter. There is also, as the top-level parent comment suggests, the point that adultery is more or less celebrated in much of popular culture. T…
The case that isn't being made is that you should be able to tell Jane about Joe in a private way. That's called discretion. And besides being the better part of valor, it is part of being a wise person.
The people who are OK with this leak should ask themselves if someone should be able to tell a wife about her cheating husband without worrying about hacking and leaks. Or even government dragnets (maybe it's a drug problem, which could be illegal).
If we make people think twice about talking to each other, there are many cases where we make them think twice about helping each other.