The class obviously doesn't require a student to handle his gun since they are demanding guns to be left in the car. So what they're really saying is that they don't trust folks to keep their carry guns holstered during class.
Unfortunately, when some guys get around other gun owners they feel compelled to jerk their carry gun out of the holster and wave it around for show and tell. For that reason, it's not a bad policy. Much like some gun shops that have similar policies about loaded guns in the store. It helps keep carry guns where they belong, holstered.
I want to lead with "I completely and totally agree with you".
But I want to comment on the context of your example and make a couple comparisons.
What you are talking about are concealed carry permit holders being responsible enough to recognize the need to leave a loaded gun in a holster until it's needed for an actual defensive shoot.
You're clearly stating something that I suspect nearly all of us will agree with - pulling your loaded concealed carry firearm out for show and tell purposes is irresponsible and just poses unnecessary risks. Same for taking a loaded open carry pistol or revolver out of its holster as well.
Many of us probably recall this particular incident - a good example of an unintentional and accidental discharge - but one that could have been prevented by 1) leaving the Glock in its holster or 2) taking proper care in re-holstering to ensure that nothing finds its way inside the trigger guard.
[ame="https://www.youtube.com/watch?v=FrJMQupYxaw"]https://www.youtube.com/watch?v=FrJMQupYxaw[/ame]
Or this one, which illustrates the problems with having live ammo in proximity to guns being sold, or displayed - as well as the larger problems of 1) not personally verifying the loaded/unloaded status of a firearm every time you hand it to someone else, AND receive it from some one else and 2) following the 4 basic rules of gun safety at all times.
[ame="https://www.youtube.com/watch?v=KUonA66btgI"]https://www.youtube.com/watch?v=KUonA66btgI[/ame]
Not only did he shoot himself, he fired in the direction of three people to his left.
It's worth noting that in both cases the accidents involved trained police officers who should have known better.
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Now the comparisons....
First, the officers in question were properly trained and should not have made the mistakes that were made. However, based on this, it's reasonable to assume that an instructor, with several classes per year, each with 10 or so students per class most of whom have less training than the above officers, would quite likely encounter a student who does something equally stupid. The fact that we don't hear more stories about students shooting themselves or others in classes is a tribute to the effectiveness of the practice of isolating guns and ammo in classroom sessions. It's not a "2A" issue, it's a "some people do stupid things" issue.
Second, most of is here would express concern about potentially loaded firearms being handled and pointed in public, non-range, non-hunting settings. You know, places like Chipolte, where the 2A demonstrators and the loaded status of their firearms are total unknowns.
My suspicion is that both issues stem from the same 2A rights over common sense argument posed by people who probably have not looked at the issues in the bigger picture with an eye to real world experiences and consequences.
Regardless of philosophical or political leanings, let's all focus on being safe out there.