Its not about nuclear weapons, ugh. Our success does come from the ability to work in groups. Not everyone works very well in groups (criminals? those guys? heh).
An armed society is a polite society. Its only irrational if you have never been the victim of a crime and just don't understand. You aren't going to convince me the cops will get there in time to protect me when I've experienced "when seconds count the police are just minutes away" since I was robbed at gunpoint.
If you want to end up as a crime scene by all means be a defenseless victim. I think around 20% of people in the USA are the victim of some sort of crime. If you are the lucky 80%, great, you are lucky. Its a terrible thing to happen to someone. If you ever find yourself with your life legitimately threatened and there are no cops around, if you can't talk your way out of the situation and you don't have a CCW, you are dead. Bang. Thats what being mortal is all about. It can actually happen to people, and it probably happens several times every day across the country.