Well let’s push that extreme a bit and see if we can come to some common ground.
Let’s say that parents have some grenades lying around. Pre-school kid picks one up, takes it to pre-school with him, blows up a few kids. Parents at fault or not? I would say yes.
I think my reasoning comes down to lethal weapons and children having access to them. I would argue that a lethal weapon is the responsibility of the parents if there are children in the house.
I would not say it’s the fault of the parents if it was a tool or something that had an alternate function that was used as a weapon.
For example, if a hammer is lying around, kid picks it up, kills another kid with it. Not necessarily the parents fault.
That’s where my line is. How about you?