Unwanted Behavior
Rather than resorting to punishment, we need to get to the root of the behavioral problem. First and foremost, if a horse's behavior is new, sudden, or not changing easily with training, we need to look at their health. Is there a physical reason for this? Most aggressive tendencies are rooted in pain or fear of pain, so we need to start here. Always have a vet/farrier/bodyworker check to see if there is a good reason for your horse's behavior.
Next we want to see if something is reinforcing the behavior. If an unwanted behavior continues to happen, we know its being reinforced, by us or something else. So what happens when the horse does the behavior? Do they get something they want from doing it? Does it prevent something they don't want from happening?
You may think you are punishing a horse by shouting, chasing, or whacking them for something, but if the behavior continues, maybe you're actually reinforcing it? Is the horse enjoying this game? Are they so bored that even bad attention is something? If the behavior continues, whatever happens after it is reinforcing (even if we think it shouldn't be). So fix this. Remedy the situation so the behavior isn't being reinforced. Most often this means ignoring it and NOT engaging (which can be so hard).
Then we want to look at the set up, can we do anything to make it so the horse can't do this behavior? If we don't want them to kick the door, can the door be open? Can we put them somewhere different? Add a barrier? Change the setting? Change things to make the unwanted behavior less likely to happen.
Then finally, we replace the behavior with an appropriate alternative. Train what you want them to do instead, then ask for that behavior in these contexts, reinforcing it with what the horse wants. If they are rushing through gates to get let out, ask the horse to walk slowly and quietly, reinforcing as you go, and then reinforce with what they want, freedom.
Health check, remove the reinforcer, change the antecedents, and replace the behavior. With these tools punishment is never necessary!