Allegedly did. You see? Comments like that are exactly the problem. Aren't we "innocent until proven guilty?" And that is why everyone is upset about Bradley Manning. He's been treated like a criminal though he's never been convicted.

How legal were the action the US gov were responsible for which Manning bravely exposed?

I don't think the US judiciary has a fixed concept of legal. The US became a plutocracy and either you are influential or not.

Thus the legality of your actions seem to depend often on this belonging and to which group the "victim" belongs.

Daniel Ellsberg did something quite similar and branding him a criminal is the wrong narrative! At least he got a trial. Manning not so much.

The US have a Whistleblower Protection Act sure, but one shouldn't care about his own well being.