The most important thing you can give a horse with a history of abuse, neglect, or any horse for that matter, is not sympathy or affection, but leadership, empathy, and good care for his physical and mental being.
Empathy is much different than sympathy. Sympathy is simply feeling sorry for him, which is not constructive. Empathy is understanding how he feels and where he is coming from in the moment. It gives the rider/handler an idea of where the horse is and how to proceed from there.