Do bits hurt horses

It is very difficult to not inflict some level of pain to a horse when they have a bit, because the bit relies on pain to make a horse do stuff. If you ever do much more than take the slack out of the reins, you are going to cause the horse some level of discomfort. If you try to pull a horse to the left right or to a stop with the reins, you are going to hurt him, and if you ever yank on the reins in frustration, the amount of pain is unbelieveable, because a horses mouth is so sensitive.

Bits on their own do not hurt horses, but when operated by a human, there has probably for every horse been some time when pain was inflicted on them by the bit.