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.
Making things difficult for the government by holding them to the light is not anti-democratic, even if the government is democratically elected.