If a person is caught driving a car with a blood alcohol level of 0.30, but by pure good luck he didn't kill or injure anybody, he is still legally liable for the criminal offense of drunk driving!His lawyers argue that the released information did not result in the death of any US troops
"Lack of harm", in other words, is not necessarily legally mitigating or exculpatory.
If Manning's lawyers can successfully show that Manning KNEW that NONE of the leaked documents were "mission critical" material whose release might endanger the lives of US troops or our allies, then the "act of conscience" defense might be persuasive. But the sheer number of emails involved (30,000+, I think) makes that line of defense very difficult. Is it really plausible that Manning had carefully reviewed every single email and could be certain that none of the leaked material could help the Taliban (for instance) plan a deadly attack?
It seems more plausible that Manning acted with extreme recklessness (at the very least!), as much so as someone who drives with a .30 BAC.