In either case, whether dealing with second-hand fear or inborn fear, the phobia is only magnified by not understanding how horses work.

In a horse's mind, there are two responses when it feels threatened. One, the most instinctual, is the flight response. Horses are natural prey in the wild. That can be validated by the location of their eyes. Prey animal have eyes on the sides of their head. Predators have them on the front.

As a prey animal, nature tells these creatures to run. That's why they were given the gift of speed and not claws or fangs. Their sharp hooves aren't all that sharp and their teeth are physiologically made for grinding grass for thirty years, not biting people.

Their secondary response is to fight. In the wild, if a wild horse is attacked or captured by predators or humans, they will run as far and as fast as they can. If the predator is, say, a wolf, they will only resort to kicking, biting, and stomping if the wolf bites a hind leg or makes any physical contact.

The same comes with being handled by humans. If a horse feels threatened, he will try to run. If he is tied by a rope of in too small of a pen, or otherwise feels no escape, then he will resort to aggressive behaviors.

Now, there are exceptions to the rule. There are certain horses more prone to be aggressive. I've dealt with those as well. But assuming that a person who fears horses won't be trying to take on one who is already showing signs of dominance, we can exclude these exceptions.