So there are a few nuanced points that I think we disagree on. Together they add up to a lot.
First, you seem to object to this leak on the grounds that "due process" forbids it. I agree. I just don't think due process should apply. The press is not the judiciary, they don't have the same responsibilities and duties.
Second, and (I think this is something wikileaks consistently fails to clarify) Wikileaks is press. They are publishing information from a confidential source. The source may be a data thief, the data owner or a whistleblower (terrorist or freedom fighter?) but that's a judgement about whoever leaked the data, not wikileaks. There are some laws and a lot of ethical concerns regarding what the press should and shouldn't publish. There are also laws protecting and empowering the press.
You might berate them for insensitivity, irresponsibility but you can't accuse them of theft, IMO.
The ethical considerations of the press are about balancing things like privacy with newsworthiness and the public's right and need to know. There are definitely emails in here that do not meet that definition. Wikileaks' model is pretty scattergun, but realistically it's the only way to get that kind of volume. I'm not sure where I fall on balance but I would be more wholeheartedly pro-wikileaks if they did a better job of selecting only relevant documents for publication.
I think this is where we disagree the most.
Third, I don't buy the idea that corporations have all rights. A violation of a corporation's right to privacy is not as bad as a violation of an individual's. That'a a whole can of worms in itself, but perhaps we can leave this as a moral disagreement.