Snowden revealed wrongdoing by people that the general public does not feel much of any sort of connection or loyalty to.
'The military', rather than 'the NSA' (both DoD, yes, but still rather distinct in the eyes of the public), is something that the American public has become convinced absolutely must be supported no matter their political stance or position on war. Support for the military must be unwavering, even if you support nothing that the military actually does. Anything short of that is un-American, therefore Manning is un-American.
