If you make mistakes while holding a gun, for your own safety, do not hold one.
It is not about making mistakes, it is about saving time. The less levers to mess with the more time you have for doing other things. You shave milliseconds here and there, in a 10 second gun fight you might have won 1 second overall.
Police do not train in real gun fights, they have training facilities where they simulate threats with real people, they don't even shoot real guns. This is what you learn at Police academy (at least in Canada). If you wanna know more about this go to the regular meetings/introductory meeting Police offer every month to give information to those interested in joining the force. In those meetings they usually show you how they train (among other things).
IDPA is not police oriented, is civilian oriented and it was conceived in USA for those with carry permits. IDPA allows regular mortals to train with their platforms for a 'rainy day', after all you want to know what to do if you are going to carry.
Long story short: How many gun fights have I been in? NONE. Ask a police man that, most of them never been in one either.
Training is done through re-enactment. You gotta re-enact the situation in a fake scenario, there is no way to re-enact the real stress but at least you exercise muscle memory, muzzle control, reloading skills and you get comfortable with your gear and that will eventually make you faster and safer.
Waiting to be in a real gun fight in order to see how you react, is plain silly.
The more training you have with your gear/platform/gun of choice the more proficient you will become. Choose your poison, I like it simple. Less is more.
If that's the case then there's no way to make an argument that under the stress of a gunfight you won't shoot yourself on account of the lack of an external safety on the glock. Nor would there be any way to predict your ability to make hits, which is a far more difficult task. If you can't trust yourself to engage the gun with a grip that will take the safety off, you can't trust yourself to do any of the subsequent and more difficult tasks, so give up now.
Besides which, of course, when you shoot a 1911 your thumb should be riding on top of the safety, making it very difficult to get wrong.
Trained drivers perform emergency maneuvers well mid-crash on a fairly regular basis.
Trained pilots do the same.
Repetition and training will allow people to repeat actions under stress that they can perform relaxed. HOWEVER, pilots, who train vastly more than 99.9% of shooters, still do things wrong on occasion. Obviously the things they do wrong tend not to be "grab the stick wrong" which would be the equivalent of grabbing a 1911 so poorly you can't get the safety off, but they do check the wrong gauge or make the wrong correction and crash once in a while.
That is why I like manual safeties. You can train enough to perform the basic tasks correctly every time - tasks like gripping the gun. You can't train enough to know that you will NEVER make a mistake. For this reason I like a bit of a margin of error. Is it manageable to do without? Yes. Would I rather have the option? If I could, yes, I would.