"[Obama] repeatedly expressed concerns that any American acknowledgment that it was using cyberweapons—even under the most careful and limited circumstances—could enable other countries, terrorists or hackers to justify their own attacks. “We discussed the irony, more than once,” one of his aides said." "Irony" is the wrong word. It's "hypocrisy".
As an analogous example, parents, knowing that many people think in crude categories such as "drugs" and "illegal," would not simply pot in front of their children without explanation. They would not want to discover later that their kids were doing meth or shoplifting and hear, "What are you angry about? You smoked illegal drugs right in front of me. How is this different?" The parents would likely find themselves accused of hypocrisy, by their kids and by others who honestly or disingenuously failed to understand the distinctions the parents drew between smoking pot and doing meth, or smoking pot and shoplifting.
I don't know if the United States has an official stance on the acceptable use of cyberwarfare, but the fact that they chose to leak their involvement in Stuxnet rather than openly admit it and justify it suggests that they have no official policy to cite (though it may also be that they don't want to officially acknowledge responsibility for Stuxnet's collateral damage.) If there is no official articulation of policy, we really are setting unpredictable precedents that are likely to implicate us in future disasters.