That was my initial thought but there are two challenges.
The first involves financial liability. Much like when a dog bites once you might be forgiven, but twice and you can be sued very badly and be assumed liable as you decided to allow a known high risk animal to be on our property. Additionally, a horse can be potentially viewed as an attractive nuisance, thus if a child or unaware adult was injured it would still be on me. Complicating this is that the person who is hurt may not sue you-it could be their insurance company, so even if it is your best friend you are still at risk.
The second aspect was evaluating the likelihood of this type of behavior being modified in the horse. His life was hard. He came from three years of profound starvation and neglect. When I got him he hadnt been handled at all. So a very poor early foundation, much like a neglected, abused child. Additionally he was from racing lines, thus very high strung and anxious by temperament. The combination of the two meant that he never really developed a good approach to coping with fear and had a very low threshold for stress tolerance before he would respond in an extreme, explosive way. Typically he would become scared of new things, then if forced to confront them, would panic, and try and get away form the scary thing via running...and forget you were near him. We did a lot of ground work and desensitization with him, but Ive consulted with several trainers since the accident and the general consensus is that it is very hard to modify these tendencies, especially given how he extreme he could be-thus he would always be dangerous and should be euthanized.
If handled and cared for from a young age, likely he would still be high strung but would have learned "self-soothing" and found alternate ways to handle stress or had greater trust in humans to direct him when under stress.
Interestingly Ive seen some trainers who specialize in these horses describe this as the horse reacting "unconsciously" or as we would describe in a jungian shadow state and use something resembling DBT to address. There are also trainers who apply a modified MBTI to horses, this fellow would have been a "aggressive fearful" animal which corresponds a highly extroverted, highly neurotic feeler. They can be very dangerous animals, albeit its not their fault how they were bred or handled.