Edward Snowden’s defenders–and, alas, he has many, even after he has shown his true colors by taking refuge in Vladimir Putin’s illiberal fiefdom–claim that he is not damaging American security but simply fostering a much-needed debate about once-secret NSA surveillance.

That’s not how our British allies see it. The chiefs of the major British intelligence agencies–MI5, MI6, and GCHQ (Government Communications Headquarters, the British counterpart to NSA)–have just testified before Parliament that his leaks have done grave harm to British security and aided al-Qaeda. The New York Times reports:

“The leaks from Snowden have been very damaging, and they’ve put our operations at risk,” said John Sawers, the head of the foreign intelligence service, MI6. “It’s clear that our adversaries are rubbing their hands with glee. Al Qaeda is lapping it up.”

Iain Lobban, the director of the eavesdropping agency, the Government Communications Headquarters, said terrorist groups in Afghanistan, South Asia and the Middle East “and closer to home” have discussed the Snowden revelations. They have assessed “the communications packages they use now and the communication packages they wish to move to,” he said, “to avoid what they now perceive to be vulnerable communications methods.”

Mr. Lobban called that “a direct consequence” of the leaks, adding: “Yes, I can say that explicitly. The cumulative effect of global media coverage will make our job far, far harder for years to come.”

Naturally Snowden and his acolytes will dispute such claims as being self-serving propaganda from unaccountable spy chiefs. And really there is no way to prove the damage Snowden has done. Even if terrorist plots are carried out in the future and innocents die, there is no assurance they would have been disrupted if Snowden had not come forward to inform the whole world of the NSA’s capabilities.

But at the very least let us not compound the damage that this arrogant traitor–who takes upon himself the role of determining which intelligence operations are legitimate and which are not–has done by curbing or shutting down the NSA’s surveillance. As they used to say after 9/11: that would be allowing the terrorists to win.