Exactly how this information endangers anyone is unclear.
As for hitting the medical oxygen tanks to destroy the plane, you'd have to be really, really lucky to do that while the plane is moving at any significant speed. And if it's standing still and you are after the President and armed with a high-caliber sniper rifle, why wouldn’t you target him directly? Besides, if you wanted to make the plane explode, it would be much easier to aim for the fuel tanks in the wings (which when fully-loaded hold 53,611 gallons). Terrorists don’t need a diagram to figure that out. But a rescuer would want this information so that the oxygen valves could be turned off to mitigate the risk of a fire or explosion.
Schneier on Security: Air Force One Security Leak