First, please don't tie a dog that climbs in a run, or anywhere near any fence for that matter, eventually they will hang themselves. I don't even put jumpers (dogs that hop up and down near a fence, in a run with a collar on).
The easiest fix is to put a livestock panel over your run, wire or zip tie it down, quick and easy.
I own 6 gsp's, and have trained hundreds, and this is not typical. Now, I only purchase from breeders, or breed my own from mentally stable parents. No hunting dog can function with this kind of temperment, especially if they are being trained and trialed at the highest levels, they just can't do it. Mine are in the yard with chickens and ducks, and they each retrieve in training, competing and hunting, probably thousands of birds a year.
Now there are poorly bred ones out there, and you admit this is the case. Which brings me to buyer education, but that is a whole nother thread!!!
Cover your run, excercise your dog (train off leash control, and an ecollar and someone that knows how to use it would be great, with very 'soft' dogs (and most dogs aren't really 'soft' they are manipulative) as you never have to physically yank or correct them) Don't baby the dog when he is acting fearfull of strangers, as Jamie said make him deal with it. As he isn't a fear biter, this isn't a case where I would say give up and euthenize, contain and train.