As they say in intelligence, most of the secret information is obtained from public sources. For example, the traitor published an order of food for a closed meeting at the embassy. He may have looked at it and found nothing of interest at all - why not to publish it? However a foreign intelligence service would be quick to note that there is only one person who might be there who likes a certain exotic food - and that food was on order. Guess what, that person was invited - a valuable information, and other people can now take it further.
To declassify something you need to know the reasons why the information was classified to begin with. Then you can check if those reasons are no longer true, and that no new reasons showed up. A single soldier in a shack in the middle of nowhere does not, cannot (or at least shouldn't) have access to all that information - and even if he does he doesn't have the attention span or skills to properly consider all the implications. Old records are declassified all the time, but it takes a lot of effort. You cannot just rubberstamp a DVD full of data as unclassified, sight unseen. This guy did just that, without authority and without a good reason. That's not how things are done ... anywhere, not just in the army.
There isn’t any reason to assume information is classified for good reason. Very often it is classified for bad reasons. There isn’t any way to have someone else decide what should and should not be, for then it wouldn’t be secret. Or, rather, it’d be less secret.
My problem is with pretending every damn thing is tied to national security. We’ve been on a war footing since 1941, basically. We’ve been at pretend war with an abstract concept—terror—and real, official war with a couple of countries for over a decade. That’s an awful long time for the mice to play while the cat is locked out.
We have to take Obama’s word, for instance, that the US citizens he has robots blow up deserved to be blown up, and didn’t deserve due process. We can’t see what evidence they used to reach that conclusion. Trust him, it’s there. We won’t ever know what the hell happened in Benghazi unless and until secrets out themselves. Maybe them worrying about tattletales is the only incentive to behave in the meantime.