If it were me, I'd throw him in a group of other more mature horses for a while so they can beat the snot out of him. You can't win this fight with him, he's bigger than you. A few grouchy mares would definitely teach him some respect.
Respect lessons by mares will not transfer over to respect for humans, and may in this instance actually make horse worse.
Anyone that works with horses and herd dynamics, will tell you that when new horses are introduced into herd, it is the ones at bottom two spots that will fight the hardest as they don't want any more bosses. That will translate in turn to a horse like this deciding to keep from having another boss when humans begin to work with it.
For that matter same with any animal/creature.
As for PWL thoughts about harsh judgement. I usually tend to err on side of caution when giving advice, as well as make comments about other's advice, simply because I do know what can happen, if for instance you tell someone to hard tie horse and leave it, never thinking that the person may tie to sapling, rail fence, portable round pen, or even cellar door.
You also have to take in to account the "amount of fight in the dog" as it were. Not dog fighting per se of course, but the attitude that handler has, and how easily they will back down if horse decides to step it up.
Much damage is done when someone "sets a battle" without having the fortitude to carry through to the other side. The slappy slappy that so many resort to with nippy/biting horse for instance. Does nothing to correct or stop, and actually makes horse worse. We see it all the time.
But nothing harsh was said to this poster. Just truths, that hopefully will be taken and used, before they end up in ER, or grave.