Mutually Assured Destruction

“Of course I carry a gun,” he boasted.
“Why?” I asked
“In case I get burgled or mugged. Someone might try to kill me.”
“Does that happen often?”
“No, not really,” he confessed.
“I see.” Seeking further clarification I asked, “But it’s happened to you?”
“It could …” he claimed, “But it won’t because I’m carrying my piece.”
“Oh, I see. It’s like M.A.D.”
“What!”
“M.A.D. Mutually Assured Destruction, like when there was all that hoo-ha about nuclear weapons. They won’t fire their missiles because they know we’d fire ours. Is that it?”
He rolled his eyes and walked off.