Are you trying to sell this to people who understand horses or non-horse people?
Horses in many ways are very sensitive animals, responding to their rider's commands, but also their emotions. Good horse people recognize that fact (and have for centuries). Someone who is concerned about their horse "abandoning" them, someone who is attuned to that, isn't going to be concerned about a horse taking a bite at him when he (or his groom) messes up.
Assuming the horse would deal with the problem by biting, it's a one time thing caused by the rider. For the rider to blame the horse requires the rider to ignore the fact that the rider messed up. That's not taking much responsibility on the rider's part and makes me think the rider isn't much of a horseman.
Realize that the majority of people in the past, and even many owners of today, are not good horse people, and blame the horse no matter how the owner screws up. I've bought quite a few horses very cheap because of this fact.
But your character is a contradiction that I'm not finding believable.
What would concern the rider in this situation is a gradual souring of the horse. The well balanced relationship between the horse and rider gradually goes south. For example, for show horses the horse that used to get blue ribbons now refuses to go into the show arena.
Now as the rider's emotions go south because of his internal stress, this can start showing up in his riding and handling of the horse, without him being aware of it. The horse, in response, starts going downhill in behavior. And all of a sudden, the rider realizes that over the past few weeks his horse, who used to be his partner, is now his enemy.
Here's where writing about horses becomes complicated. Many writers have to use horses because it's part of the background to their world. Many try to incorporate the horse into the book not understanding horses. This leads people like me, who understand horses, to enjoy a good laugh.
This isn't to tell you whether you have a good idea here or not. I do like the idea of a rider realizing how bad his life is through his horse. Most readers won't have problems with your scenario. But I thought I should mention the risks you incur. It's hard to do this stuff good enough.
Best of luck,
Jim Clark-Dawe