Perhaps I overspoke a tad. I'm awfully skeptical is better put.
We're largely a scientific community here at HN. Something is False until proven True. You may have a hypothesis, but it's just that, an educated guess as-to the result.
To prove something True you must present overwhelming evidence. We have none of that here... What we do have is a hypothesis being perpetuated as fact in the face of almost zero concrete evidence.
The FBI first says "there is zero evidence to suggest North Korea has anything to do with the hack". Then some "high level anonymous White House official" "leaks" to the NY Times that they believe it's North Korea, and it takes the FBI 3 full days to change their public announcement, yet present zero concrete evidence. This was a rudimentary hack against a private company, there's nothing that would be classified or kept top secret here. Sony should do a full disclosure. Until then, we can not be certain of anything.
You seem to be awfully certain. Frankly, I have no idea and am quite skeptical of people who profess such certainty in the face of so few facts. Seems to be the kind of thinking where you have a conclusion and look around for facts to support it.