I agree about the possible reasons for reticence to share "black" technology.
And I certainly do not want any valuable national secrets blabbed to the world.
But when you state: "Any technology shared between Keyhole and Hubble would become public knowledge...", I have to wonder if that's necessarily true. I don't know why NASA scientists are incapable of going through the same screening that DOD scientists (and DOD contractors) go through. If there was a will to share tech, I think we could find a way to do it without jeopardizing national security.