This isn't just about US foreign policy. Let's take a different example that removes the interventionist "bad smell" of the NK example. Let's talk peace.
E.g. Imagine A and B want to negotiate a peace treaty. They represent large and diverse constituencies. Officially, they're not talking to each other -- there is ongoing violence, and hard-liners in both the A camp and the B camp will replace the A or B negotiators if they are deemed to be too soft.
So, there's a secret summit of A and B negotiators. Publicly, neither side can budge. However, because the talks are secret, the negotiators are free to make initial concessions to get the ball rolling.
How could making those talks public possibly be a good thing? It might actually scuttle peace and result in more violence.
It's easy for rogue elements to spoil a sensitive negotiation. There is a real need for secrecy in order to have productive negotiations on sensitive topics.
Your example relies on the idea that government negotiators will be more benevolent and peaceful - will work more towards the common good - in secret than in public.
Maybe that happens once in a while. The far, far, far more common case is that secret negotiations amount to a conspiracy by the powerful against the weak.
You comment assume that the hardliners are wrong, and that the negotiators should talk behind their backs. Without knowing what they talk about, how can you know that?
E.g. Imagine A and B want to negotiate a peace treaty. They represent large and diverse constituencies. Officially, they're not talking to each other -- there is ongoing violence, and hard-liners in both the A camp and the B camp will replace the A or B negotiators if they are deemed to be too soft.
So, there's a secret summit of A and B negotiators. Publicly, neither side can budge. However, because the talks are secret, the negotiators are free to make initial concessions to get the ball rolling.
How could making those talks public possibly be a good thing? It might actually scuttle peace and result in more violence.
It's easy for rogue elements to spoil a sensitive negotiation. There is a real need for secrecy in order to have productive negotiations on sensitive topics.