ASPEN, Colorado – The former commander of the Afghanistan war and the most elite unit in the U.S. military wants to use robotic aircraft "a lot." But retired Army Gen. Stanley McChrystal actually sounded more like a skeptic of the U.S.' robotic arsenal during a talk to an elite audience. McChrystal sounded notes of caution about both the lethal and the non-lethal functions of the U.S. robotic arsenal.

"We can look at things and get an extraordinary ability to see things," McChrystal told CBS News' Bob Schieffer at the Aspen Ideas Festival, a meeting of U.S. economic, political and media elites. But McChrystal, who revolutionized the Joint Special Operations Command's intelligence operations, said drones provide merely "one part of an understanding. We need to understand what drones are not."

Drones are no substitute for information derived from human beings, the former commander emphasized, on the ground in dangerous, confusing places. McChrystal reminded an audience that isn't particularly familiar with the U.S. military that for all hype about the sophisticated drones – Schieffer, a news anchorman and talk show host, casually asserted that the drones are "very effective" – they can't peer inside buildings or assess an enemy's intentions. "I hope we don't use them to the exclusion of teaching people [foreign] languages, [and] sending people to live" in foreign countries, McChrystal said.

And their ability to expedite killing the wrong people is profound.

"We made a huge mistake one night in Afghanistan," recounted McChrystal, who's now a lecturer at Yale University. "We killed a civilian farmer in the middle of the night with an attack helicopter based upon [intelligence] we had from an aerial platform. The guy was digging by the side of the road." Mistakenly believing that the farmer was planting a bomb, the U.S. military ordered a helicopter strike, only learning later that the farmer posed no threat.

McChrystal remembered apologizing to Afghan President Hamid Karzai, who informed the then-commander about Afghan irrigation techniques which sometimes involve tending the soil at night. "That's the point: you have to know those things," McChrystal said, as drones do not remove the need to "get your feet in the mud and understand people."

McChrystal actually dodged the subject Schieffer wanted him to discuss: the expansive use of killer drones in Pakistan, Yemen, Somalia and elsewhere. But he subtly critiqued the drone strikes while he praised the May 2011 SEAL Team Six raid in Pakistan that killed Osama bin Laden. There's a "perception" that the U.S. prefers to kill from a distance, McChrystal said, which much of the world considers dishonorable for not putting its own servicemembers lives' at risk; the bin Laden raid served as a potent counterexample.

Schieffer didn't challenge McChrystal's points. (Among them: it's time to "consider a draft" to take the burden of waging the nation's wars off the backs of 1.5 percent of the population; and the greatest threat to U.S. national security is poor education.) The Aspen Ideas Festival – which, full disclosure, paid for my attendance – is not a place where people talk truth to power. Before McChrystal spoke, Atlantic magazine owner David Bradley allowed the former Pakistani dictator Pervez Musharraf to defend his 1999 military coup and even compare himself to Abraham Lincoln. Aspen is a place where elite perspectives gain yet another megaphone.

Still, one of those elite perspectives was an evidently sincere appreciation for one of the U.S. military's most consequential generals of the 9/11 Era. McChrystal stepped off the stage to a rare Aspen standing ovation.