You do not live at the whim of a primal defense mechanism. Mastering your own actions and responses is what seperates us from the apes. Personally, I have higher aspirations than dragging my knuckles and licking ants off a stick.
I think you understood my post perfectly, you've just not seen the other side of the argument.
You are confusing two issues; Training and phisological responces. Sure, if you train and train to always go right to the slide release chances are it woln't be a problem for you when the poopie hits the fan (unless, of corse, it's wet, dark, you're injured, the slide release lever breaks off, etc This woln't prevent you from activating the slide release, but will certinally make it more difficult).
As you said the training conditions you to deal with the phisological responce. Sadly, however, the vast majority of gun owners don't train. They buy a gun, shoot a few rounds (25 to 100) every once in a great while and never take a class, dryfire, do walk-throughs, or anything. They've purchased their magic shield and they are safe...
For those folks, the chances of them finding that little slide release when the crap starts to fly are slim and none (assuming they even make it that far into the fight).
And none of this adresses that with my hand, I can't reach the slide release without shifting the grip on the gun. In the middle of a gunfight the last thing I want to do is be looking down at the weapon and shifting it around in my hand. With the slingshot I can keep a eye on the target, rack the slide and require the target.
That's just what works for me. If someone honestly trains and shoots enough rounds that they can instinivley find the slide release every time without looking then it's not a problem either. But your whole point hinges on people training enough to deal with the phisological responces when the facts show that most people don't actually do that.