Nicolas Weaver explains how a “defense wins” policy in a combined offense and defense environment doesn’t sound not very convincing (case in point: the NSA reorganization).
Instead, NSA seems intent on ensuring that they will never be trusted again. The objective reality is this: from the perception of those outside the government, merging the IAD and SIGINT missions is tantamount to eliminating IAD entirely. Trust is a matter of perception as much as reality. “Defense wins?” Whatever the actual truth, for now, the rest of the world says “HA!”