2. With the hammer dropped and a round in the chamber, it doesn't take must of a bump or knock on the back of the hammer to cause the gun to discharge. (My friend and I actully tested this. With the gun fastened on a shooting bench and on condition II, he hit the back of the hammer with a empty magazine a few times and it caused the gun to discharge.)
If the hammer is fully decocked, it rests on the firing pin stop and the firing pin is pushed flush into the slide. There is no way for the hammer to impart any force onto the firing pin - period.
The only way for the gun to have discharged under the conditions stated is if either the firing pin spring was removed/insanely weak (in which case the inertia of the blow caused the discharge - something that would have just as easily occurred in Condition 1) or the firing pin was way out of spec or the gun was on the half-cock notch and not actually fully decocked.
actually with the hammer sitting on the FP energy can still be transfered to the FP. Though an extremely unlikely event, theoretically it is possible to transfer enough energy to move the FP.
Can't. Happen.
I dunno why this doesn't seem to be obvious, but if the hammer is down IT IS NOT RESTING ON THE FIRING PIN. It's resting on the firing pin stop, and the firing pin is pushed into the slide (without coming out the firing pin hole in the chamber, since it's too short). No energy imparted on the hammer will directly cause the firing pin to move. The only way that the firing pin can move is via inertia - a blow to the back of the gun can cause ANY firing pin to move fore/aft in a pistol that does not have a firing pin block, occasionally with enough force to cause a discharge. This can occur regardless of hammer position - cocked or not - since the dynamics in question have everything to do with the inertia of the firing pin and nothing to do with the hammer.
This is why Condition 2 is the safest way to CARRY; the hammer cannot possibly fall and hit the firing pin. (This is also why you should never carry on the safety notch, aka half-cock, because if that notch breaks the hammer CAN fall and cause a discharge and the thumb safety cannot stop it.)
Lowering the hammer is not safe and it also requires recocking which is also not a safe procedure especially if done under stress.
I agree fully with the latter part of your statement, and so did the US Army (who asked that the thumb safety be added specifically to keep troopers from having to decock under stress).
However, I do not believe that manually decocking a pistol, under normal circumstances, is so fraught with peril as to be untenable. I do it all the time.
If you're not comfortable doing it - then don't. But you probably shouldn't make blanket statements that manually decocking a pistol is patently unsafe, because it can be done quite safely if one has a mind to learn how.
Getting to Condition 2 is less safe (from an AD perspective) than flicking on a thumb safety. Carrying in Condition 2 is more safe (from an AD perspective) than relying upon the thumb safety.