Tercio, The story you tell is alarming. That nowadays such scenarios can be present in a commercial livery stable beggars belief. From what you write, the horse is mentally disturbed and as such is obviously very dangerous to both visitors to the yard and to the workers on the yard.
Such horses can present to specialist horse trainers an object lesson but whether the animal can be cured of its misbehaviour in general towards humans and other horses is a question way beyond my level of expertise to answer.
In the UK I doubt if I could find a farrier to shoe the animal or a vet to inject it.
The HF.com is probably not the place to discuss such a situation.
Velvet - be safe and walk away.