The punishment has to fit the crime and has to match intensity for intensity. Additionally, it has to fit their knowledge base. I am more stern with those who know better.
So - called up a friend who regularily foaled out 50-79 mares a season and she said you nip it in the bid now, while she is small or you will be very very sorry if you allow it to continue
I have found that if you over-react the first time they try something really naughty, there typically won’t be a second time. So, while the punishment should fit the crime- remember that some crimes are major felonies, and that includes biting and kicking. It may not hurt (actually they often don’t make contact the first time) but the intent was way out of line- so go after them! I’m not advocating abuse, but I have seen the way horses treat each other when they mean business, so I have no qualms about smacking or “biting” with my fingernails or even using a whip (if that’s what required for my safety) on a young foal.