The difference in public perception between Snowden and Bradley Manning is interesting. Is it because of the nature of the information leaked? Is it because Snowden got away, and some folks like to root for an underdog?
Snowden leaked particular information for a clear purpose. That material has changed political discourse and public perception.
The vocal majority in the US are racist, xenophobic nationalists, and are disgusted by the idea that any conceivable US initiatives would be even slightly compromised for the sake of any number of foreigners, anywhere. The gender-change was a nail in the coffin - because to a lot of the public, that others him into a foreigner too.
Snowden is very middle-class professional, dates a (female) model, races to Moscow through Hong Kong like a movie spy, and the President of Bolivia was pulled out of a plane just to find him (unsuccessfully.)
(American) people generally understand their world in terms of shallow stereotypes and movie narratives; they hate both subtitles and protagonists that aren't white middle-class heterosexuals.
Manning is a lot more of an underdog than Snowden.
You don't get to decide that ;)
I think you'll find transgenders, et al, having to live the lives they do, have developed a far more nuanced take on public perception than fits with the role most of their self-styled allies have assumed on their behalf.
One of my first patients was an HIV positive stripper who presented with shingles. During the history, I noted the off-label estrogen and the B cup and asked "Darren, what pronoun would prefer?" "He is fine, but whatever makes you comfortable" he said.
'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.