first off kick, biting, etc IS FORCE in the horse world, their warning signs are pinned ears, a lifted leg and the swishing of the tail, etc.
The reference to Ceasar Millan was because he uses what dogs understand to deal with them. He doesn't EVER go straight to force on them. Which is the same as what us horse people should do, understand your horse and their signs before you "punish" them.
And no, you shouldn't go straight to punishing them. There are other methods that smacking but unless a horse was beaten before a smack here and there isn't going to hurt them or effect how they see you.
16 year old TWH Mare named Ginger
3 year old APHA Paint Gelding named Fox.
RIP Evie (Clydesdale) 7.29.09 & Magic (OTTB) 2.23.10