I meet a lot of folks with dangerous horses who experienced a specific "training program."
While one program may work for a horse, but other horses may need things to be adapted in how and what is presented. But "trainers" often look for physical responses to specific tasks and have a pre-set "step 1, 2, 3" agenda. This causes them to lose perspective or are unable to recognize what is influencing the horse's thoughts, and not believing his concerns. Often rushing or bullying begins to try to get him to comply with the task accomplishment focus.
As the trainer continuously increases pressure towards the horse- physically or spatially- they get upset or critical when the horse becomes overwhelmed when he physically explodes.
I'm 5'2" and there's no way I can "make" any animal do anything. I often talk about influencing a horse's thought first, then his movement. This can contribute to the safety of both the human and the horse. If the horse's brain is already fleeing, defensive, concerned, or fearful, and I ask MORE movement of him, what will his response look like? It is like adding fuel to an already burning fire.
But when following a "set" program time is not allowed for the horse to learn how to think through a scenario, nor is acknowledgement offered when the horse tries. If someone has been taught "it" has to "look" like "x,y & z," anything less is not accepted by the human. This contributes to the horse "trying" less and looking for ways to avoid any interaction.
I believe horsemanship and the quality of it comes back to the human's education first. Becoming aware of our own human behavior patterns, thoughts, intentions, slowing down and becoming mentally present, our energy, anticipation, and communication. So it can be a "hard sales pitch," when a trainer isn't offering easy, quick fix solutions or guaranteed performances, rather than having anything to do with what the horse needs.