You have spoken in a clear, concise, and convincing manner. Well done! You’ve swayed this person.
And you are of course correct in your implication we need to begin design and production of the AR16 posthaste! A gun that shoot through 3 walls is the clear solution. Well done sir!
But in all seriousness you are correct. A nation littered with mentally unstable morons and high-powered rifles is a potently and predictably tragic way to be.