How have courts treated government predictions of harm to a government employee's freedom of speech?

"[W]e have consistently given greater deference to government predictions of harm used to justify restriction of employee speech than to predictions of harm used to justify restrictions on the speech of the public at large. Few of the examples we have discussed involve tangible, present interference with the agency's operation. The danger in them is mostly speculative." (Waters v. Churchill, supra, 511 U.S. at p. ----, 114 S.Ct. at p. 1887.)