They know absolutely nothing about guns. For all they know, guns go off voluntarily without anyone there to pull the trigger.
So for all those of you who don’t know, a cartridge consists of the bullet, the gunpowder, the casing or shell, and then the primer. The gun’s firing pin strikes the primer, which ignites the gunpowder. This causes an explosion that ejects the bullet out of the casing and through the barrel and out the muzzle. In most firearms, the casing is then ejected either automatically or after the bolt action is pulled back.
The question should have been titled “Who’s dumber than a political activist who creates an ad that demonstrates their ignorance of something they know nothing about?