I don't think you're looking at the problem the right way. There was never any doubt terrorists exist, and that there's nothing they'd like better than to kill us. There isn't any doubt lightning exists, either. It can strike anywhere, any time. This doesn't mean I'm going to give up the right to go outside whenever I damn please to be "safe" from the small chance that I'll wind up falling victim to a lightning strike.
Actions like those described in TFA and what they say about us as a society are, as far as I'm concerned, a cure that's worse than the disease. And "knowing where to stop", in my view, is something citizens should be discussing and deciding for themselves. Paramilitary organizations with an interest in increasing their power and control shouldn't be unilaterally making such decisions for all of us.
As a law-abiding Canadian citizen, my odds of being killed by a cop with an attitude problem are a lot higher than my odds of being killed by a terrorist. So to my mind, the "kooks" are those who willingly trade freedom for the illusion of security, and cede their right to decide how much freedom to trade in without even a debate.