You know this would be a kin to having a house on the corner of two very busy streets with cars zipping by in all directions. With the child standing on the curb the parent sets in the house and calls out, "don't go out in the street it is dangerous".
By faith Noah,being warned of God of things not seen as yet, moved with fear,prepared an ark to the saving of his house;by the which he condemned the world,and became heir of the righteousness which is by faith Heb.11:7
Well, it's more like pointing out the curb, streets and traffic that the kid might not have paid any attention to otherwise. If the mother hadn't notified the kid of the gun that they were too young to understand much about, they may otherwise have ignored it.
Obviously that's not a reliable safety - firearms shouldn't be left out AT ALL around children. Carry it, or lock it up - period!