I worked for a reining horse trainer, a real trainer not a monster in disguise.
The man I worked for worked his horses, but never, never did a horse return with bloody lip or mouth.
I am positive of this cause it was me who brought the horses back after a training session to clean, groom, bathe and take care of them, so I had first look at their body.
Did cinch issues happen, occasionally
and they would happen quickly when the animal was ridden for an hour and it was hidden under the cinch..
A bad reaction to the material of the cinch happens...just like humans can have allergic reaction to certain materials so can the same thing happen to a horse. You address it immediately and properly.
To continue to ride so it is now a raw, weepy and soon bloody mess is
inexcusable and cruel to the animal.
He is no trainer if he subjects his mounts to such treatment as is shown by how the horses react to him.
Shut down is a good term...reactive is a good term and at some point reactive and explosive in reaction may also become a good description.
Please make sure you stay safe and the animal know it is you if you touch him...speak to them
cause they know voices and know kindness and who is cruel and hurts them...at some point this "trainer" shall reap what he gives in return by his mounts...
Make sure your barn owner is absolutely clear that this "trainer" is to never handle your horse under any conditions, ever!
If the B/O asks you why, tell him what you have seen... Facts only, no embellishing of facts needed.
The facts are damning enough.
No one can go against what your feelings are with what you have seen and now know is truly wrong, unneeded and a better way to communicate with your partner does exist.
If this was my barn and I was alerted to this treatment of animals on my land
, I would be having a discussion with said "trainer" about changing his training practices or he will no longer be at my barn...get out. Watching him closely would now be part of my daily routine...a barn owners responsibility and right.