I got a reaction similar to yours from the "it's fine" crowd about being "able to do it". I agree the issue has nothing to do with competency of what's in actuality a trivial action, I just can't for the life of me understand the bravado behind the thought process. If there's a .1% chance of something catastrophic going wrong vs. a 0% chance, give me the 0% all day long when there's nothing to gain by taking the .1% chance. If I ever "have to" make a weapon safe I'm going to use the safety, the decocker, or remove the round from the chamber. I'm not going to put my finger on the trigger of a loaded weapon I don't intend to fire.
I agree with you that if you NEED to make a gun safe, you can use the safety, use the decocker, or remove the magazine and round from the chamber. (I only have one decocker-equipped weapon, but it is decocked when it's put down or holstered.)
You're concerned about the difference between a .1% chance of an accident than a 0% chance, but that is -- for people debating relative safety --
a bit like medieval clerics arguing about how many angels can dance on the point of a pin. I've seen MANY MORE (unintended) unaimed discharges at a range that are potentially dangerous when people practice live-round presentations from the holster than .1% of the first shots fired otherwise.
And that said, why must we automatically assume that a slip while decocking will be catastrophic? If the gun is pointed in a safe direction, it won't be catastrophic. It might just be embarrassing.
In this type of discussion, attention is always paid to the possibility of the hammer slipping from the shooter's grasp as it is lowered, and but almost no attention is paid to where the muzzle is pointed. As long as you have a gun with a loaded chamber pointed in a safe direction as you manually decoc -- perhaps with the muzzle pointed toward the ground away from your feet -- even that worrisome .1% becomes irrelevant. If your hand somehow slips and you discharge a round, the only thing at risk is your ego -- and there's a good chance that the hammer will hit the safety notch on most guns, and not discharge! More importantly, if after the hammer has started to move, and you release the trigger, the firing pin safety may be reengaged. (If the hammer doesn't continue to drop easily, you just gently press the trigger again to lower the hammer a bit farther, and then release the trigger. as it continues on down.)
There may be a few cases where you might HAVE to go to fully hammer down on a loaded chamber. Shooting in IDPA Stock Service Pistol or USPSA Production with a non-decocker CZ or Witness is one example: in either gun game you must start with the hammer fully hammer down.
This is true even though a decocker-equipped CZ lowers the hammer to the safety notch on the hammer -- a half-cock position like in 1911s -- neither of those organizations -- which are intensely focused on gun safety -- will let you, if you're using a safety-equipped CZ, Witness, or one of the Turkish knock-offs of the CZ design can be legally manually lower ed to that same half-cock position when starting a string in a match.
If you can safely manually lower the hammer all the way, it seems logical that you can also safely lower the hammer to the safety notch. I don't understand their reasoning, but I always do as required. Never had a negligent discharge, either.
I've noticed, too, that nobody ever voices concern about drawing from the holster and firing at a target at a range. We all need to practice this skill if we're concerned about using our weapon in self-defense. Having shot at local indoor ranges for many years and having been a safety officer at many IDPA matches for a number of years, I've seen many more misplaced first shots than NDs while decocking; in fact,
I don't think I've ever witnessed a negligent discharge while a gun was being decocked, either in matches or elsewhere. People who decock manually -- and not many do -- are generally pretty careful.
It seems that most of the folks who are concerned about accidents while decocking have never owned a non-decocker weapon. And they've never had a desired to become comfortable with what is a relatively simple process. The idea of a POSSIBLE accident totally colors their attitudes and behavior. That's okay. But their attitudes don't have to control everyone else's attitudes. and behaviors. They don't want to manually decock, they don't have to. But just because they think it's unsafe doesn't make it unsafe.
Then too, as I've noted in these types of discussions before, if you shoot at an indoor range, pay attention to all of the holes in the ceiling, or marks in the floor or on the wall... hardly any of those shots intentionally hit where they were intended. And those potentially dangers discharges are seldom mentioned.