This is not a difficult line drawing exercise. Lawyers do it all the time: you’re protected from disclosing client confidences. But it’s highly illegal to actually assist your client in obstructing an investigation!
Whose morality, ethics, and common practice? The fact that this leaked and almost nobody cares means that people have made a decision. They want the government to have wide latitude to protect them from terrorism, and they care more about that than prosecuting this purported wrongdoing.
Most people have made the decision that the government is corrupt, Assange is an asshole, and there's nothing they can do about any of it because their elected officials are also corrupt.
That is hardly an endorsement of all the horrible things that the US government has been secretly doing in their name.
The US executed people for torture after WWII. (None of its own people, though. That is acknowledged as an unfortunate failing.)