In their native language, horses learn from the sharp and concise actions of lead horses or higher ups in the herd. If a colt marches up to an adult and promptly lays into it using his teeth, you can bet the other horse isn't going to gently push him away; as was mentioned earlier. My question to you is, why do you think we should do the opposite of what any other horse would? We hear all the time that we're "partners" or that we're "our horses leader" but if he's biting us or otherwise disrespecting us - are we really? Pushing the horse's face away is a slap on the wrist, it doesn't have a consequence other than the pathetic "Pony don't do that!" and it leaves room for more error, making the horse potentially dangerous. Watch a horse perform the swift kick and everyone laughs, watch a human do the human's equivalent of the swift kick and it's automatically abuse. There's a point where a line Must be drawn for us to have strong consequences for strong actions. .. I digress.
A horse's natural language is body language and pressure. It is used all of the time for every situation. Whether the situation is pinning its ears and snaking a mare away from another stallion in the wild, or pinning its ears and snaking everyone else away from the food in a pen. This is something they know, understand and respect. It's something we can very easily translate into human in order to speak with our horses, please see: lunging. It's an easy game really. You apply pressure until the horse moves off, you release pressure and let the horse continue moving and you add pressure back when he misbehaves. We're not patiently nagging a horse to do what we want, are we? You don't stand idly by the horse's hip and tell him to walk on several times over, calling it quits and walking away when he doesn't move, do you? Unless you're standing in the center pointing to the left and using a baby-voice to tell your horse to move, your answer's no. You get snappy, you want something and you want it now. You have just turned into the lead horse. Are you abusing your horse though?
In lunging not moving has a consequence of being chased or having rope thrown at the hip. When biting, people who get "nasty" (like 12 yr old tlking did) give a consequence as big as the bite. In leading, people who get "nasty" will back a horse off using increasing pressure until a foot goes back and nowhere else. Most trainers I know are happy with just a step back, but they're not patiently and gently tugging the rope backward. They're getting big and they're doing it fast. All of this pressure is something a horse understands. It's the native.
The foreign language is stuff a horse -wouldn't- naturally understand and that is where the patient, slow approach is necessary. Things like pulling a cart or being tacked up and ridden around a ring. A horse's natural instinct when galloping isn't to gallop around a 2-acre circle. They learn quick but it's still a strange topic to them. This is where I found (when I was learning to train and watching my instructor train too) the most patience was necessary. My instructor didn't have to get harsh when the first saddle when on and the mare threw a bucking tantrum; she also didn't have to get harsh when the mare's first instinct on the first canter out in the big arena was to go through the grooming area. My instructor corrected her by lunging her or by turning and pointing her back into the arena, where pressure consequences still applied. She learned quickly. Did my instructor abuse the horse? Likewise, when I was learning to train an unruly school horse who was known for charging, biting, and running into and ahead of people walking him I had sharp consequences. I whacked him on the nose hard for biting me and leaving a bruise (when the original response was to push him away), he never bit again. I got up in his face when he tried running me over after a tarp spooked him, he lead quietly after that. He used to charge people in the paddock when they went to catch him, so I charged at him back like a wild person, flailing a lead rope and making all sorts of "squeals" to get him away from me, he didn't charge after that. He's still used as a lesson horse, he's not head shy, spooky, and his ears are almost always forward. Did I abuse him?
Just remember that every action has an equal and opposite reaction. For charging, biting, and leading poorly, the horse was almost always rewarded at the grooming station or ignored - what he wanted. It was opposite of what he did, but it wasn't equal. When the tables were turned on him, he gave me what I wanted and my old lesson barn needed. His consequences were huge but he learned, just as he would have in the herd.
Yeah, used incorrectly, bits can be bad. Spurs, crops and whips can be bad too. But it's my experience that most horse people I've met are a lot more enlightened then people are giving them credit for. It's a matter of learning how to ride properly, being given enough time on the ground with a horse to learn how things work from both perspectives, and being given the room to learn how to ensure a horse is a safe partner.
Regardless, I agree with some of your original points. There needs to be positive reinforcement, and the release of pressure is almost -always- that positive stuff they look for. I'm not throwing an apple at the horse's head while we're lunging to reward him with the hopes that he eats, enjoys and understands why an apple was thrown his way. We do always end on a positive note. The positive "tone" of my voice is used as a vocal reward when something is done perfectly on his part. It's just a matter of balance and being able to show restraint in keeping consequences from turning into abuse.