IMO, there are a number of people who are going to be dangerous, whether they have training or not. They forget their training, don't practice enough to stay competent, or become so familiar as to become lackadaisical.
Sometimes they buy guns. Even without a permit.
Sometimes they carry guns.
The gov't lets them drive on the road every day.
Some otherwise responsible people have had no training. And that isn't a good thing.
I like what Arizona did. Add firearms to the high school curriculum, so everyone
has exposure to training. So that when he buys a gun at a garage sale, is showed one at a friend's house, finds one where it shouldn't be, or decides to get a carry permit, he is already trained in firearms safety.
BTW, last I checked, FL had a requirement to "demonstrate proficiency with a firearm". When I took the class, they made me fire one shot at maybe 7 feet. So not much of a (practical) training requirement.