Whoops.
Although I've pretty much distanced myself from the gun boards recently, I was called into this one from afar.
You forgot the other half of that law, oldfart. The one that says that bodies at rest tend to remain at rest.
A muzzle down discharge on a concrete or similarly hard, tough surface would bring the bullet to an immediate and complete stop, the same as it would if fired straight into a concrete wall. If the bullet even clears the muzzle...on which I have a few doubts...it would flatten out and lay there on the floor...inert and harmless because once it stops, there's no force available to cause it to accelerate again.
At most, it would bounce three or four feet high and fall back to the floor...the same as it would if fired into a steel plate as most of us have seen. It certainly wouldn't retain sufficient energy to cause a fatality.
And if the muzzle struck at an angle that would have let the bullet keep going...which is unlikely to cause an inertial firing pin strike...it would have skidded along the floor at a low angle, endangering a foot or maybe even an ankle at most.
This claim tends to put most of everything else you've said in question.
On topic...
There was no intent by Browning or anyone else to continuously maintain the pistol in Condition One. It CAN be of course, but it wasn't specifically meant TO be. If there was any intent at all on Browning's part, it was to use the half cock as a manual safety.
And once again, I will fade back into the shadows.
Cheers all,
T