That, of course, is only true if the mugger's potential victims are mostly disarmed either by choice or by legislative fiat--it has no validity when most of a mugger's potential marks are armed.
People who argue for the banning of arms ask for automatic rule by the young, the strong, and the many, and that's the exact opposite of a civilized society. A mugger, even an armed one, can only make a successful living in a society where the state has granted him a force monopoly.
Then there's the argument that the gun makes confrontations lethal that otherwise would only result in injury. (cont)