I wouldn't put him off as stubborn. I've met many more scared horses than stubborn ones. What is stubborn anyway? Do horses really not want to do things just to piss people off? Nope. Horses aim to please. This guy probably thinks these poles are unsafe, or that it's a better idea to go around then, etc. His reasoning probably makes sense to him, so don't get mad at him.
He may be scared, but he may show fear in a different manner than other horses. When afraid, some horses run and rear and spit fire... And other horses "shut down", dissociate, and lock up. He may be locking up out of fear.
Walk him up the pole in hand. You should know how close he's going to get before he wants to stop. Walk him just shy of where he always wants to stop and let him stand there. When he's comfortable, ask for another step. Get him there step by step.
Or walk him in circles around the poles under saddle. Make your circle smaller and smaller until you're almost walking over it. Get him close, and then take him away in a bigger circle. Approach and retreat. Eventually, make a very tight turn and see if he even tries to step over the pole. Reward that try. Work for small successes.