They don’t have a say. So should they ever be used by humans? For work? For sport? For pleasure? Made to live “unnatural” lives in ways like having their feet trimmed, being fed grain, or being put in a stall? How far do you want to take this line of reasoning?
I don’t support abuse in any way, shape, or form. But nor do I support the myth that every moment of training involves harmony and rainbows. I don’t support the myth that any amount of contact on the reins, anything that is not strictly “classical,” anything that puts the slightest amount of pressure on the horse is abuse.