Bob,
You make a comparison between proprietary limits on free speech—such as when a company requires that an employee not divulge specific information about its internal operations—to the authority of the armed services to prohibit its servicemen from voicing their opinions about a specific military assignment. An employee of Coca Cola, for example, has no right to reveal the formula for their product to the general public, because it would clearly damage their competitive standing. The employee voluntarily restricts his own freedom of speech by contract. That is a very specific and delimited contractual restaint.
To insist that a serviceman who voluntarily enlists remain silent when he feels that a given assignment is unjust is not really comparable. Foe one thing, you are taking about a much broader restriction. Preventing someone from expressing an opinion is radically different from prohibiting him from disclosing specific information. A noncontroversial comparison could be made to valid prohibitions against a soldier releasing specific information about his platoon’s planned maneuvers to the press.
As to the soldier’s right to express opinions, I think a reasonable restriction would conform to the ‘clear and present danger’ principle offered by Oliver Wendell Holmes in Schenck v. United States:
"The question in every case is whether the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent. It is a question of proximity and degree. When a nation is at war, many things that might be said in time of peace are such a hindrance to its effort that their utterance will not be endured so long as men fight, and that no Court could regard them as protected by any constitutional right."
Although that faulty decision involved a civilian draft protester and was subsequently modified, I think it spells out a fairly decent guideline as to what speech, whether public or private, should and should not be prohibited once an individual joins the military. To say, as you do, that a soldier has “consented to hold his tongue while in service” suggests that he has become, in effect, a second class citizen, and that goes way beyond any reasonable limits imposed out of just concern for the safety of his fellow soldiers or the success of his mission.
Incidentally, I would certainly disagree with Holmes that this “clear and present danger” principle should be extended to the general population. I agree with Henry Mark Holzer that speech alone does not rise to the level of treason and should not be legally restricted or suppressed for the "common good."
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