d4g that a very good summation of what happens. When you are born in and raised in that closed atmosphere you really do not understand reality at all. Being forbidden 'worldly' friends, and discouraged from reading non-JW books or having further education you have no way to break out of that false reality.
Because of being forced to be weird by the no holidays, no joining in policy of WTS, everyone at school and work makes you feel misunderstood and even disliked which fuels the paranoia.
They shun because they sense that a person who no longer believes is a threat to their understanding of reality. No words need be spoken about "The Truth" at all. The fact that an intelligent person no longer believes is enough for them to go running to hills to find their known "reality".
Yes when they bump into us the fight or flight mode sets in rapidly. Cognitive dissonance has them fleeing from us in terror because we represent a reality that just does not compute and causes them extreme discomfort.