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Unlike the U.S. military post-Vietnam, where senior officers are supposed to be moral role models, the CIA—that is, the Clandestine Service, the engine room of espionage and covert action that has always defined the agency’s ethos—has been much more relaxed about these things. The drama surrounding David Petraeus’s extramarital affair with Paula Broadwell could change all that. Ever since the agency director’s resignation, a small army of pundits has taken to the airwaves, warning that infidelity could be exploited by foreign intelligence services and used against American officials. The pressure could force new standards for the intelligence world. That would be a mistake. As morally upsetting as it may sound, we should all want the typical philanderer...