A neighbor-hating dog is not uncommon, but it can turn into a real problem. It is the job of the owner to establish peace between the dog and the neighbor.
There is certain dog behavior that is desirable in some situations, but reprehensible in others. For example, most dog owners like the sense of security a dog's bark provides when a stranger rings the doorbell. However, agressive barking at your neighbor's three-year old daughter playing in the backyard can be alarming, for both the neighbor and the owner.
Telling the Difference Between Friends and Strangers
Dogs are naturally territorial, which is one of the main reasons some canines display aggressive tendencies towards people with whom they are not familiar, including neighbors. A dog that growls and barks uncontrollably at the sight of the next door neighbor stepping out to greet the paperboy every morning should be scolded. Just like any other training the dog receives, he or she will eventually understand the difference between a neighbor and a stranger.

How to Deal With a Dog Who Hates the Neighbors
There are several ways to deal with a dog who hates the neighbors. First and foremost, it is important to address the issue directly with your neighbors. Apologize for your dog's behavior and assure them that you are working on the problem. Depending on the neighbors, they may be willing to come over and meet the dog on your property. This allows the dog a sense of security while meeting the neighbors. Once the dog is familiar with them, they are less likely to bark or growl at them every time they set foot outside their house.
Dogs are sociable animals who generally like people. Teach your dog to tell the difference between friends and strangers before a full-out feud develops with the people you live alongside everyday. At the same time, make sure to be understanding of your dog and the reasons for his or her behavior; the dog is probably just trying to protect you and your home. Until the problem is resolved, do not let your dog run loose unless he is confined in the yard; that will be seen as a threat by your neighbor, and won't help the relationship. Treat both your dog and neighbors with care and respect to control a situation in which your dog hates your neighbor.