I think all trainers should consider themselves responsible to make it clear that not all things can be fixed wth work. Some things, like understanding your horse, evovles, if you will, from the times when you are feeding, grooming or watching them react to others in a turn out paddock.
As a rehabilitator, I am one of the biggest foes of abuse.  I don't abide by it, I don't allow it and I will not let it go unchecked.
Now here is the thing that a lot of folks don't get.  When my horse bites me, if I slug him and bark NO! does he really hear the no part, or is he still on the "Wow, that hurt and why is mom so angry?  I was just trying to tell her my leg hurts."?
I've dealt with biters, viscious kickers, maulers and knuckleheads.  When bitten the first time, it's in reaction to something that I as a trainer am doing.  Instinctively, I will slap a cupped hand right on the side of the mouth.  Two reasons, a cupped hand makes noise and does not inflict pain.  It gets attention when added to a NO!  The other reason, an assault at the forefront of the muzzle, could damage something.  Depending on the age and how hard you are hitting.  Slugging, well, tell me, last time a 3 year old little boy hit you, did you slug him?
I know folks are going to say, a horse is bigger, they need to know they are a horse.  You have to put them in their place.  Well, yeah.  All of those things.  But you do not have to inflict pain or discomfort to achieve anything you want.
What you do have to do is have yourself centere, before you try to center your horse.
We need to let go of our fears and learn to accept our horses as they are.  Fear is what controls a lot of our own emotions and reactions.  It's the same for a horse.
Sorry, you asked for it.  I gave it.  Not always pretty, but well, heck, toss some paint on it, add a few sashes, it might just not look bad in a little better light.

I had that problem with my stud.  I was slapping him on the nose.  I posted a thread and got advice. To throw a fit back at the horse instead of hitting ( from Kar ) and it helps.  The last couple says he is starting to back down.  I still want to get him on the nose, but I don't do it.  He is really starting to listen to me.  I can see a big difference from smacking him to stop the charging- to throwing a fit to stop him.  The fit works so much better because it is not so much challenge as hitting him.
V.R.
Denver, CO.
        
Hey Kar,
Thanks again for the help, he really is starting to behave himself.
V.R.