The Joker explained it well. People are not afraid of violence, we habituate to it very easily and it's everywhere. They are afraid of unpredictable violence.

That homeless guy is going to die of hypothermia from being out in the rain? Makes sense. He should try to get out of the rain.

Thousands of women are killed by their ex-boyfriends every year? Makes sense, some guys are crazy. Good thing I don't date guys like that.

Someone might bring a gun into Starbucks and shoot random people? Good lord what is the world coming to! Take all the guns away! Islam! It's those creepy loners again!