I've read most of the posts, but some of what's being said reminds me of a video taken in Pakistan I believe of a horse who fought back!
Go to YOUTUBE and search under: ANIMAL ATTACK - horse attacks guy in retaliation!
This is crazy, the horse (pony) was under so much pressure (they're beating it with stones I believe) from these men that it went berserk and attacked them.....I hate to think what happened to the horse afterwards:(
I personally haven't seen a horse 'attack' in a round pen incident or anything similar. I have seen them attack randomly, no pressure at all because they were sour in the barn and extremely fit (in a herd, the fittest and strongest wins and leads) and I found that the fitter the horses would get, the more extreme their behaviour would become......albeit they were racehorses, no necessarily bred for temperment.
I've had horses back up on me or turn their butts to me on the longe line, usually young horses who are just confused with what im asking them to do, usually in those cases I would drive them away from my with the longe whip (occasionally they got popped because they started backing up on me......not safe!) but as soon as they moved I would remove eye contact, lower my whip or arm and relax....and there fore they would relax too.
I think you've made some progress, and I'm glad you had a better day