I get most of the examples, but I think what criminals are the most afraid of is to lose control of a situation.
In case of a robbery or minor crime, if the guy points a gun at you, last thing you want to do is reach for yours... He will want to shoot you to make sure he's not the one killed. So a minor crime (lost of money usually) turns into a homocide.
Both have valid arguments, reasonnable people will use their weapon only under extreme cicumstances. Problem is there are not only reasonnable people. And the fact someone's ok one day doesn't mean he will stay saine all his life.
I travel a lot in the US for my job, and I always had a great experience with people and enjoy talking to see the different point of views throughout the country on many subjects. We tend to forget that people from Canada are not much more different than someone from Boston is from Miami, Houston or Des Moines. We can't generalize how people are in Canada or in the US, both are huge countries. Look at Europe, dozens of country on a smaller land.
I never felt threatened in any way. But there was a common factor: when watching the news, they present it so you feel this is the last day on earth, always a ''breaking news''. The coverage looks like what I saw on 9/11 here in Quebec. I remember feeling like WW3 was about to happen. The coverage was done in a way to show the gravity of the situation. I feel like the way news are presented (today, not on 9/11) are not appripriate, they want to make you react to keep your attention.
Too much of that and it is normal to become afraid to be the next victim.