Earlier quoted context omitted.
I think the line is on whether it's a personal/private matter and when it's not. The NSA is a government agency, so what it does is in the public interest. A guy planning to bomb something is also by definition affecting the public so exposing that is also in the public interest. This hack, the fappening and similar are completely personal and private so they are of no concern to anyone but the people involved in it.
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.
Or they could be cheaters who are lying to their SOs.
Regardless, we the general public have no horse in this race. We haven't been asked by the person's SO to find this out, the people in question are not public figures, and we have no knowledge of the specifics of their situation.