At that point, you just shoot them and say “You know what … you’re absolutely right … that wasn’t an accident, I had to do it deliberately, like I said I would — my bad.”
But …
It’s Natural Selection in action and, fundamentally, they should not simply be allowed to self-select for elimination from the genepool but actively encouraged.
In fact, given that people are a combination of Nature and Nurture, being born of idiots and then brought up by them simply perpetuates the problem, so they should be encouraged to let their kids play with them first, thereby bringing an end to their line before they go on to ruin the World for the rest of us in their turn.
What the US needs is a programme of adverts in which children are encouraged to play with guns like they were toys. Then, sensible people will think themselves “I don’t ant my child killing itself and/or its sibling(s), so I won’t have any guns myself” whilst the stupid will eliminate themselves from the genepool.