> As far as I can tell he thought he was doing the right thing at the time
That’s what he said, that’s not necessarily what was actually true. I no longer believe him given his subsequent actions.
> Surely the support for his actions indicates to you there are people out there who would have done what he did
If you’re suggesting that there could have been genuine patriotic whistleblowers, I agree. But Snowden’s actions have proven he’s not genuinely patriotic but a supporter of a genocidal regime.
> to me being a traitor has connotations of deliberate intent to do harm due to some kind of external loyalty
That’s not what the word means. Betrayal of country can occur for any number of reasons, for instance ego or greed are often involved.