So WikiLeaks founder Julian Assange is guilty of “a reckless action which jeopardizes lives.” That’s according to John Kerry, on this week’s unauthorized release of a huge tranche of State Department cables. Confronted with a previous Wiki-avalanche, the senator took a more sanguine view: “However illegally these documents came to light,” he intoned in July, “they raise serious questions about the reality of America’s policy toward Pakistan and Afghanistan.”

The latest WikiLeak may ultimately amount to no more than a colossal headache for U.S. diplomats. By contrast, the previous leak exposed U.S. sources and methods on the battlefield. Yet the senator somehow finds the prospect of an embarrassed State Department more troubling than the exposure, to the Taliban’s vengeful gaze, of Afghan informers—another instance, I suppose, of John Kerry reporting for duty.

Still, every fiasco must have its silver lining, and this one is no exception. For starters, it has belatedly prompted at least some liberals to grow up on the topic of government secrecy and its connection to national security, international stability and, not least, human rights.

Take the Obama administration, whose condemnation of the July leak was leavened by the self-serving observation that most of the documents dated to the Bush years. The administration was also at pains to reject any comparison with the Pentagon Papers, the publication of which remains a pillar of liberal self-regard.

Yet if there’s a salient difference between the Pentagon Papers and the WikiLeaks disclosures, it’s that the Nixon administration went to court to prevent publication, whereas it was only yesterday that President Obama ordered a review of security procedures for handling confidential documents and his Justice Department opened a criminal investigation into the leaks. Couldn’t the administration have acted sooner, particularly since, as Mr. Kerry has belatedly noticed, lives have been put at risk?

But better late than never. Last week, State Department legal adviser Harold Koh sent a stern letter to Mr. Assange’s lawyer warning of the “grave consequences” that would flow from publication. Alas, none of the consequences had anything to do with Mr. Assange, which might explain why the letter had no effect. But given that this is the same Mr. Koh who, as dean of Yale Law School, pompously lectured the Senate Judiciary Committee in 2008 about the evils of “excessive government secrecy,” his letter still represents a significant change of heart.

Speaking of changes of heart, one also has to wonder what effect the WikiLeaks disclosures might have on other articles of liberal policy faith. Are Israeli Likudniks and their neocon friends (present company included) the dark matter pushing the U.S. toward war with Iran? Well, no: Arab Likudniks turn out to be even more vocal on that score. Can Syria be detached from Iran’s orbit? “I think not,” says Abu Dhabi’s Crown Prince Mohammed bin Zayed, who added that Syria “would continue hedging on key regional issues (Iran, support for Hezbollah, peace process) for the foreseeable future.”

Has the administration succeeded in pressing the reset button with Russia? Hard to credit, given Defense Secretary Robert Gates’s description of the Putin-Medvedev regime as one from which “there has been little real change.” Is the threat of an Iranian missile strike—and therefore of the need for missile defense—exaggerated? Not since we learned that North Korea had shipped missiles to Tehran that can carry nuclear warheads as far as Western Europe and Moscow.

All this is enough to make me hope for a more grown-up foreign policy from the administration—and nearly enough to tempt me into applauding WikiLeaks’ disclosures. But not quite. We shouldn’t need WikiLeaks to settle policy differences. Nor should it have required another round of WikiLeaks to make the administration take secrecy seriously. What really matters for the successful conduct of U.S. foreign policy is confidence, a word that simultaneously denotes trust, secrecy and also betrayal (think of the word “con”).

What WikiLeaks has done is use the betrayal by the original leaker to expose American secrets and thus destroy trust in America’s reliability. For an administration whose policy choices have already done so much to erode global confidence in the U.S., these leaks are a disaster.

How should the administration go about regaining confidence? It’s astonishing that Iceland, a member of NATO, is where WikiLeaks is headquartered. Don’t we have an embassy there? It’s astonishing that the Australian government has yet to receive a request from the U.S. to take action against Mr. Assange, an Australian national. It’s astonishing that Pfc. Bradley Manning, the suspected leaker, has yet to be court-martialed. It’s astonishing that Mr. Assange should be described by National Public Radio as a “whistleblower,” while in fact he’s conducting a form of cyberwarfare against the United States.

OK, that last one isn’t so astonishing; some liberals never grow up. Then again, some do. What a pity so much damage had to be done before that could happen.

Write to bstephens@wsj.com