Again, I have to agree with Cherie.
Any horse who has been abused will only associate those tools IF you use them as such. Take the time, desensitize, and retrain the horse's frame of mind.
My mare was terrified of anything resembling a whip, crop, or handystick at one point...not any more...I took the time to desensitize her to them and showed her that they are not items to be feared, nor are they items soley for the principle of discipline.
If you think there are other ways of sensitizing this horse to new stimuli, other than just 'doing it' so to speak, Society Joe, please, don't be afraid to share. But my years of training horses have shown me that ***** footing around any horse, especially a scared (and in this instance, also defensive) horse only keeps him fearful. When you yourself act 'scared' you tell the horse with your body language that there is something to be afraid of. Act normal, train normal, and leave the past behind...you will have a better horse for it.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."