I think we're reading way more into posts than was intended. While some have indicated that a lot of training is not necessary, I don't see that to mean training is not helpful.
What we have is two situations: those that buy a gun because they have a perceived need for protection but cannot afford expensive training and those that have a gun(s) and can afford expensive training.
The facts, not opinions, are that a very large number of people, in the millions per year, have successfully defended themselves with a gun with minimal training.
What we don't know at this point is how many times a civie tried to defend themselves with a gun and were not successful but would have been successful if they had had some training. But some training (some as opposed to none or a weeks worth at a school) may not help at all against ambushes, assaults on a sleeping person, etc.
Then there's the perception that awareness born from training circumvents deadly confrontations from the start. And I think there's truth to that. But taken to the 'limit', if maximum training gives us the capability to avoid confrontations, then we won't need to carry a gun, because we will be able to evade and escape.
It really comes down to simply this: Is a person better off with a gun and little training or better off without a gun? From the past performance indicated by findings in the article, and according to the study that shows guns are used over a million times a year in self-defense, it is strongly suggested that people with guns and little training are doing quite well.
Because I shoot so frequently at a public indoor range, I see lots of people shoot. Most simply can't shoot. I think that fully agrees with rscalzo's observations, "Way too many have no idea what they are doing, nor do the follow the basic rules of safety. Many of these people have carry permit yet do not have clue one what they are doing."
While I fully agree with his observations because I see the same thing myself, it is undeniably working. We are not seeing large percentages of accidents with firearms that the massive numbers of gun ownership would imply. And we are seeing the huge successes of untrained persons successfully defending themselves.