Wilikeaks is a painful, but necessary step forward. Eventually, the walls must come down. It's a natural process in human evolution, for us as individuals and societies to grow more able to face and deal with our own reality, not lash out when it's revealed to others against our will.
The most harm, we are told, has been to our relations with harsh undemocratic regimes. With their trust in our confidentiality diminished, they will be less likely to share with us things that they know make them look bad, and that they shouldn't be doing in the first place, such as being deceitfully cozy with their non-democratic allies.
In the short run, revealing such truths may work against our foreign interests. In the long run, it's a big step forward for human evolution.