Most who carry a gun daily have discovered that having lethal force available makes you go out of your way to NOT need to use it. Being legally unaccountable can override that, hence the problem with police violence.
That said, there are definitely exceptions, those whose lack of impulse control or moral compass turns them into ticking time bombs.
Is that predictable and preventable? Possibly partially. Is it worth the prior restraint implied in that prevention? Not to me.
Realize that there are lots of concealed guns, guns you will never see, everywhere you go except controlled access spaces with metal detection at entrances. This is a good thing; most will never be used aggressively.
Self defense is not optional behavior. Choosing to not be prepared to defend yourself is choosing to be a victim. And legislation can change that as easily as it can change gravity.