The thin veil of "civilised" society

[Razoromero]

Does anyone else ever find themselves wondering at the thin veil we live under and just how fragile it really is? You could be patiently standing in a queue for instance, people in front of and behind you, some more patient than others and you start thinking "WTSHTF all this would vanish." That person moaning behind you would now be a potential threat, possibly determined to take what you have. You'll say 'no' but will they take 'no' for an answer? You may have to defend yourself, your family and your supplies with lethal force.
How many people in that queue would turn nasty? How many of them would you have to kill to survive? What does that mean in today's reality, the fact that total strangers who are polite and nod hello to you would, in another reality, want to fight to the death to get their way?
In fact, who could you trust in a major SHTF aftermath?
It's amazing how quickly the veil could be torn away. Would it ever come back?