It kind of sounds to me like that horse should never have had the bit in its mouth yet anyway. If the horse is not responsive with ground work and doesn't know pressure yet why in the world back it and expect it to know what the trainer wants with a bit in its mouth? I just think the horse needs more work on the ground and the trainer got way too frustrated b/c he/she didn't do the proper ground work and got 100% respsonse on the ground before jumping on with a bit. I just hope this experiance has not messed up this poor horse it doesn't take much to make a horse not trust someone or something.