As someone who works in the defense indistry, I can testify that it matters not even one iota what I think about the importance of classified information and how it might affect the world's balance of power, period. That is not my decision to make, and it wasn't the Rosenberg's decision to make back then. Something that on its face might look totally harmless can be pieced together with other information that can lead to people getting killed. They got exactly what they deserved, and so does anyone who betrays their oath to their country.
Try to arrange for a hitman to kill somebody. It won't matter if he's successful or just an undercover cop; the caller will still be guilty of attempting to have someone murdered.