I guess it is paranoid. Nothing bad happens to good people right?
It's called self preservation. Animals have it. Watch them when new people come about. Watch how they check out the situation and the person and then decide if it's safe or not.
God gave us the same ability, to check out the person and then decide. And then to pick up on the aspects that give us concern.
Better safe then sorry has always been my motto. How you chose to do what you do, more power to you. I will not condemn your decisions, I really wish you wouldn't condemn ours.