Earlier I was asked how to get a dog to stop "hating" cats. This is tricky because it isn't necessarily "hate" that is causing the dog to do this. One of the reasons for this behavior is that dogs are predators and they can have what is known as a "prey drive." It can also come from past negative experiences with cats. This behavior can be adjusted, but timing is critical. Give the reinforcement too soon and you increase the behavior. Don't use a strong enough reinforcer and the dog doesn't care.