If it's that clear that Snowden did the right thing, why not pardon him? I feel that not pardoning Snowden is roughly equivalent to making a statement that people should be in the dark about the government's spying programs, and that the government should be free to spy on its people, unchecked.
That's been the clear attitude of both the Bush and Obama administrations, illustrated through many actions completely unrelated to Snowden.
Let's say they pardon snowden, in the future, if more whistleblowers appear, all they have to do is say "but snowden was pardoned!" And then what?
The proper response by the government to future cases is to judge them each case by case.
I really wish, but it won't. The system is solidified.
If they open this door, and then do anything against people using Snowdens precedent, the white house will be in a much worse position than now.
The US public is not stupid. There is very little goodwill towards Manning about what he did compared to Snowden[1]. And for good reasons.
So people are pretty good from separating whistleblower and leaker. So I think it will be non issue.
[1] There is a lot of sympathy for Manning about the way he was treated, which may or may not be a good case for clemency in the next administration.