Governments (should) set their own moral compass. It is important that government employees are ethical and moral. But they are not contracted to provide government with ethical or moral advice. While policy advice to government must never be unethical or immoral, the critical determinant is that advice be framed within the construct of the law: governments are required to act legally. So also are government employees. If government employees entertain ethical or moral qualms regarding the actions of government, especially in the contested areas of the military use of lethal force, the law enforcement use of armed force, or the possible intrusion into personal privacy by the intelligence or law enforcement agencies, they have a duty to make their concerns known to those who exercise the principal accountability to government. Institutional leaders have the responsibility to exercise their judgement and advise on these matters. If a government employee remains conflicted, he or she is absolutely entitled to resign. But government employees are not entitled to advertise their dissenting views. Nor is there any self-imposed "duty" to inform the public of perceived government misdemeanors. In a democracy, government employees exercise their rights as citizens to vote governments out of office. Manning and Snowden broke the law. That is why the US court has prosecuted and sentenced Manning. And it is what should happen to Snowden and anyone else who acts outside the requirements of the law.
This was a fascinating discussion.
However, I must say that I found Allan Behm's assertion that intelligence operatives/defence personnel etc should only concern themselves with the legality of their employer's (in this case the state) actions is naive and flies in the face of post WW2 attitudes.
Effectively what he seemed to be promoting was a silent protest through resignation - an act that is only partially better than 'the Nuremberg defence' for acts of gross immorality. You simply cannot expect people to uniformly accept this.