Technically, he is.
But that's like calling someone who has killed a cop a "cop killer." Facts are facts, but they don't automatically make someone a bad person.
Essentially, Snowden did betray his masters' trust. Is he a traitor in the true sense of the word? Sure. But it doesn't bother me a bit.
Judge Andrew Napolitano says that if Edward Snowden ever faces a U.S. court, he may try to argue that his oath to the Constitution is higher than his oath to the government to keep classified information secret.
Well it depends, he swore an oath to the constitution*. What he found was in violation of the constitution (4th amendment). Ultimately the constitution trumps any other oaths/contracts made to other gov. agencies. If this is the case, the NSA is the traitor.
As for the NSA being a traitor for violating the 4th amendment, yeah. I suppose that's true. But using that rubric, all the charlatans who infest D.C. are traitors, as are their many bureaucratic lapdogs.
Here, we have the Senator from SC, after watching the media reports, thinking he may be able to score a few points with the common folk if he used some of his political weight to lean on the Russians to send this traitorous fugitive back to the US to face justice:
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