There are numerous signs that Wikileaks had an important influence in the events in Tunisia, Egypt, Bahrein and Syria.
> Didn't Americans democratically elect a government which estimated that keeping diplomatic cables secret was the right thing to do?
Assange isn't an American citizen, therefore he can't be a traitor to the USA.
> Didn't Assange publicly release those cables?
Yes, and ironically they significantly enhanced the opinion that the rest of the world has now on USA diplomacy and policy. So it actually both profited the USA and the rest of the world.
> That being said, he certainly promoted freedom of speech.
Exactly. Some people (like me) states that social forms of freedom are more valuable than anything else. Some others value authority, or morals, or other things higher.
You could take the "political compass" test to know better where you're situated. I myself is in the bottom left, a rabid leftist-anarchist; I'm quite sure that Assange fares quite similarly.
It might not seem so at first, but I'm a hardcore libertarian which believes that the way towards greater freedom and transparency is through peaceful persuasion and respect for the law.
Though this is true in general, sometimes the particular circumstances command that you break the rule, i. e. do wrong. I recently mentioned Kant's analysis of the problem :
http://news.ycombinator.com/item?id=2529104
Nixon's democratically elected government estimated that keeping Watergate secret was the right thing to do. I would suggest that Woodward and Bernstein promoted democracy by releasing the information publicly.
Making things difficult for the government by holding them to the light is not anti-democratic, even if the government is democratically elected.
The greater principle (perhaps not made clear by my example) is this: Don't trust governments. If they choose to keep things secret, it may not be in your interest, but theirs.
In relation to your questions about the law, I recommend that if Assange has broken laws or been violent, then he should be apprehended and charged. I agree with the rule of law.
I'm actually not aware that he or his organization have broken any laws in relation to publishing these cables. It's been six months now, and no charges have been laid. I'm aware that whoever leaked them to Wikileaks probably did break the law though, but that is not related to the suggested prize nomination.
Didn't Americans democratically elect a government which estimated that keeping diplomatic cables secret was the right thing to do?
Didn't Assange publicly release those cables?
That being said, he certainly promoted freedom of speech.