This guy was uncouth and mistress Valeria and mistress Monica were pissed at how he acted and were ashamed to be associated with him. They took it upon themselves to punish him and get him to change so they turned him into a human pony and let him feel the pain and the humiliation of it all. Because that is what eventually led to him changing the way the mistresses wanted.
These mistresses did not care what this guy did. They ignored him but when he became rude to them, they could not allow it. He had to be taught to stop being rude to others and the mistresses did it by using pony play mistress to do it. He was turned into a human pony and he had to carry them all over and endure their whipping and caning, which was brutal.