A stable dog shouldn't be like that. In my opinion, the dog either came from a place that never exposed him to the world OR the dog simply has weak nerves genetically OR both. With rehabilitation (exposure) by a handler that is NOT nervous or anxious about the issue, but one that goes through an environment with confidence and calm reassurance (do not play up on the "its ok" stuff, but passively say "come on" without expressing frustration), one can certainly make improvements in the dog's response. "Monkey see, monkey do."