Biting is the ONLY time I would ever strike a horse's face, and I do so then because the discipline makes more sense to the horse if it's related to the offense and the body part that gave offense. When a horse paws or kicks, I strike the leg that pawed or kicked, if they bite, they get swatted on the mouth.
If the farrier actually struck your horse full on in the face with a rasp, either side, there would be blood or visible damage. I suspect the farrier's discipline was much closer to appropriate than has been described here.
went to get a hay net to keep him busy while he was having his feet done and to my horror he was smacking him with his rasping file ON HIS FACE. I told him to wait while I tied up a hay net as he proceeded to explain to me that the horse was nipping at him. Um, that's why I told him to WAIT. This horse is perfectly willing with the farrier when he has something to do...
There is so, so much wrong with this description. The farrier arrived prepared to shoe. Why weren't you prepared? Are you going to compensate him for waiting time? Nipping or biting is always a horrendous disobedience, it's not situational, it's never acceptable. And a horse should stand quietly for handling without bribery or "something to do." If the horse doesn't stand quietly for the farrier, he needs more training or a different handler, not "something to do"
Good luck in your search for a new farrier.