It is a joke. Just look at the Abu Ghraib trials or others where they were not tried for torture, murder and rape (which they did) but for 'dereliction of duty' or 'illegal discharge of a firearm'.
They are good 'ol boys and the military will protect them with such a show trial they would usually get a death sentence or at least life.
But Manning is not a "good 'ol boy", he broke the unwritten rules. And like in some cheap mafia film, he is going down. Preferably with as much publicity as possible. (anyone honestly think he could ever be let go? how long would he survive?)
They are only trying to get him to confess about the connections with Assange because he is their real target.
They will not stop from doing whatever possible to pin the tail on that donkey. Not like the military, nor their government, really is an honest bunch that would never fake stuff and lie to get what they want.