"I may be being simplistic in my understanding of the equipment described, and I share in the heart-felt expressions of sadness posted here, but shouldn't there be an over-speed lock on even thinking about engaging an air-brake / stabilizer device on such a craft as this?"
Actually an under-speed lockout, it's meant to operate at a minimum speed of mach 1.4. I don't know; even with airplanes, you have everything ranging from fully manual controls and minimal instrumentation (well cargo planes), to an Airbus where the plane just won't let the pilot do anything considered out-of-range. Manual controls are more prone to human error; but automated controls are complex and have to at least account for possible intermittent or permanent sensor faults. A human can react easily if a reading is dropping low or 0 every so often due to bad sensor wire; an automated system, you wouldn't want to have some controls start cutting in and out because of this. This is after all a test flight so I'm not surprised it wouldn't have this yet. I also wouldn't be surprised if the next one didn't at least lock out the tailbooms until it's past mach 1.