We have two large dogs (one VERY large) and a cat, and Connor on occasion will do something mean, like pull a tail, kick "at" the animal (but not really make contact). I ALWAYS correct him right away, explaining that we are gentle to ALL living things. To enforce this, we visit the pet store often and let him learn how to handle a variety of animals, we also visit the zoo to talk about the different animals and touch the ones that we can. Connor is only 2, so a little bit of experimentation with being gentle, but it sure seemed to work with Ian, he is very gentle to all animals, and not afraid of any (but does know to have a healthy respect of them). Neither of my boys have any significant behavioral issues, so I'm not sure if that impacts things at all, I assume it does, but constant exposure to lots of different animals might help. Try reading books about animals, and talk about how you would pet the animal gently, etc.