Most of my media colleagues seem to think Edward Snowden is a saint and proto-martyr. Their Hollywood-style story line is that the fugitive National Security Agency contractor has bravely exposed American spy agencies’ tricks and mischief. But the theft and publication of secret documents is not a heroic campaign. At best it is reckless self-indulgence, and at worst sabotage and treason.

Mr. Snowden has not proved systematic abuse by the NSA or partner agencies. Moreover, his story has been told naïvely and hysterically, with a huge dose of hypocrisy and with gravely destructive effect.

Espionage is inherently disreputable: It involves stealing secrets. But enemies of the West—notably Russia and China—are spying on us. Our agencies defend us from them—and help catch terrorists and gangsters, too. But the media’s sensationalist and misleading interpretation of the stolen documents has weakened security relationships among Western allies; it has corroded public trust; it has undermined the West’s standing in the eyes of the rest of the world; and it has paralyzed our intelligence agencies.

Mr. Snowden’s allies—the Snowdenistas, as I term them—lack the skills to keep the material safe, or redact it to limit the damage. Their claims to the contrary are not credible. Moreover, they seem oblivious to the idea that we in the West have enemies and competitors. Yet if we suffer, they gain.

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Anti-Americanism in Germany and other European countries is now ablaze. The Russian-Chinese campaign to wrest control of the Internet from its American founding fathers (meaning more censorship and control) has gained momentum. Western protestations of concern for online freedom and privacy ring hollow. The reputation of the biggest Western Internet firms has taken a pounding for their supposed complicity in espionage. Their rivals are gleeful.

Mr. Snowden’s cheerleaders brush that aside. Instead they demand to know what right U.S. agencies have to bug and snoop. The answer is simple. America’s spies—unlike those in most countries—are responsible to their elected leaders, and supervised by judges and lawmakers. The U.S. has taken the most elusive and lawless part of government and crammed it into the world’s toughest system (too intrusive, in my opinion) of legislative and judicial control. America and its closest allies have the world’s only successful no-spy agreement. A list of countries that would trust Germany or France not to spy on them would be rather shorter.

The question should be put in the other direction. What gives the Snowden operation the right to leak our most closely guarded, hard-won and costly secrets?

For the damage done by Edward Snowden dwarfs the impact of Cold War traitors and defectors. Western agencies now assume that the NSA material is in the hands of Moscow and Beijing, or will get there eventually. Many worthwhile intelligence operations must be shut down or started anew: A serious spy service does not risk lives on the hopeful assumption that the other side will not exploit its blunders.

I accept that a debate is overdue on the collection and warehousing of metadata (details about the location, duration and direction of a phone call, but not its content). If you know who called a suicide-prevention helpline, and from where and when, the contents of the call matter less than the circumstances. The NSA may have deliberately weakened the hardware and software sold by American companies in order to be able secretly to exploit those vulnerabilities. If so (and the charge is unproven), it was a tactical triumph but a strategic error.

The Snowden story is full of puzzles and suspicious twists and turns. Snowdenistas are extraordinarily paranoid about the actions of their own governments, yet they and their media allies are strangely trusting about the aims and capabilities of the government of Russia—where Mr. Snowden arrived so oddly and lives so secretly.

He and his allies are not conscious Russian agents. But history gives plenty of examples of indirect Kremlin involvement in Western political movements. Like the antinuclear movement of the early 1980s, Snowdenistas see their own countries’ flaws with blinding clarity and ignore those of repressive regimes elsewhere.

Far too little attention has been paid to the political agendas of people such as the bombastic Brazil-based blogger Glenn Greenwald, the hysterical hacktivist Jacob Appelbaum and the WikiLeaks founder Julian Assange, who cloak their extreme and muddled beliefs in the language of rights, liberties and justice. Their actions are bringing about the greatest peacetime defeat in the history of the West. That is not a noble crusade.

Mr. Lucas is a senior editor at the Economist and the author of “The Snowden Operation,” a Kindle Single available on Amazon.