I'm with Fionn. No way is it in the public interest to release full details of the CIA agent concerned.
And given that it's a federal crime to do this (as I understand from the news), the identity of the people who passed the information on is very much a matter for the courts to know. As the example above of "there's a bomb on the train" say, you need to weigh up whether the people who gave you the information are worth protecting.
As much as people may dislike it, the prosecutor is right - promising confidentiality does not absolve you from responsibility. If you keep schtumm, you are an accessory to whatever was done by the people you're protecting. That goes for doctors and priests as much as journalists. Priests can at least claim "higher authority", but doctors and journalists have no such justification.
Some journos may say it's the thin end of the wedge to total loss of confidentiality in journalism. But the other way of seeing it is as the thin end of the wedge to total loss of protection in dangerous jobs such as intelligence, undercover police work and the armed forces, which will cause the death of the people exposed in many cases.