1) If a horse reared and ran off, kicking and whipping while yanking on the bit will result in more rearing most likely.
I have always been taught for rearing to be stopped you have to do two things...regain forward momentum (do what it takes to get the animals moving forward, possibly kick or whip) and once progressing forward, bend them through the neck and back and go back to the basic circling (if horse is defiant or fighting the basic bit give, it may require the jerk of a rein) until the situation is diffused enough and back at a calm level.
2) Kizer said that the trainer "lost their temper", it's never a good idea to lose your temper. When you stop being objective you're no longer training, you're abusing.
I totally agree, you have to maintain "training" mode and keep your focus. The goal is to gain understanding by the horse, not fear. But, Kizer was relaying a story from someone else, so did that person just interpret the situation wrong because they don't like seeing what needed to take place, or was it in fact an abusive situation?
"Also, if this horse was green it should be in a nice, easy bit...no twisted wire or bike chains, right? How hard does someone have to pull to split a horse's mouth open with the bit?"
Totally agree...I only use snaffles for riding my youngsters, and have luckily avoided all likeness to the initially described scenario. Green horses have no business in any harsh bit, but we don't know what type of bit it is, and even a snaffle can cause a cut if it pinches the lip and bars of the mouth.
Unfortunately, I have put a welt on the a$$ of a horse...he had (from his huggy feelie owner) developed a habit that when he was told to go and he didn't want to, he just started backing up. The owner would get frustrated and get off him when ever he quit on her. After a some time of this she asked me to get on and get him going forward, and he didn't like it. Started throwing a tantrum, and backing really fast...it took a welt on his backside and a series of good over and unders with the reins to make him realize I was serious and enough of the BS.
"Whenever working with a horse you want to use the least amount of pressure necessary. Horse's should be sensitive and responsive."
I totally agree, if a fly can condition a response, we should be able to do the same with slight inputs.