Let’s play a game.
Imagine you need to walk to your car in the dark. There are 100 men in a grocery store and you will see 10 of them separately on the way to your car. And you know one of the 100 will try to rape you if he sees you in the dark.
Simply walking yields a 10% chance of being raped. Pretty terrifying.
If you ask a random person to walk with you it might be inviting the rapist to accompany you! That’s really scary too. You’re actively giving the rapist the access to rape you!
But rationally, you’ve reduced the probability of rape from 10% to 6% (including the 50% * 10% probability that the non rapist stranger will lose the fight in the parking lot).
If you invite two strangers you double the chance that you invited the rapist! But the probability of rape falls to 3.5%. Three and you get a 1% chance of rape. If you invite all 100 shoppers with you the chances fall to near zero.
“Mass gun ownership” is like inviting people to walk with you. There’s a chance that you’re inviting a rapist along, but statistically the more people are “armed” with access to you the less likely rape is. And as terror attacks in Europe have proven, Guns can either be obtained illegally (Paris) or other means can be used (Nice). Both those attacks occurred in a country with far stricter gun control than the US, and both claimed more lives than the recent Las Vegas attack.