It's just like with Communism. If tomorrow morning every person on earth magically became a full fledged communist, theres a good chance that we will progess. Significantly even.

But it only takes one person to tear the whole system down. One person can ruin communism without even trying because communism doesn't plan for assholes. Same with weapons. If every last person on earth decided they don't want them any more we would have a lot less dead people. But it only takes one to think otherwise and suddenly we are slaves that get killed for looking the wrong way.