Allow me to illustrate with an example. Every few months, I would visit a little whitewashed school in the hills of Indonesian-occupied East Timor. The young teacher who ran the school would cheerfully bring me into her office, and we would chat about small things while her uniformed students would serve us homemade buns and strong coffee in chipped porcelain. Once the students left and the office door closed, the teacher would open her desk drawer and with a shaking hand give me horrifying photos of disinterred bodies. The Timorese resistance would dig up the fresh graves of torture victims, take photos for evidence, and pass them through their underground networks to this teacher, who would then get them out of the country through me and other diplomats. With that information we knew what the Indonesian military was doing in secret. We could better confront Jakarta, and we could assert more pressure on them to stop.
When we sent the reporting cables back to the Department of Foreign Affairs, they were secret for a reason. If they were published in The Globe and Mail instead, I would have been thrown out of the country in 24 hours and the Indonesian officials would not have permitted a replacement. The local politicians would have hired a rent-a-mob to stone the Canadian embassy. Their leaders would have told the Jakarta media I was a liar and would have blamed the Timorese for feeding me calumny. And the police would have arrested and killed the young teacher before the week was out.