The only problem with small breeds is their owners! Too many small dogs have behavioral problems because their owners treat them like small, cute stuffed animals instead of dogs. Many times they think it is funny when their 2 lb Chihuahua acts aggressively toward a stranger.
All of my dogs are treated the same, from the German Shepherds to my mini dachshund. Whether your dog is 2 lbs. or 90 lbs. it is still important that your dog realizes that you are Alpha, there are rules that must be followed and you, as Alpha, will correct the pack family for any misbehavior.
When you do need to correct your small breed dog, it is still important to remember that any correction you give to your dog should impact him/her and the behavior that you dislike stops. The difference is the amount or type of compulsion that is necessary. To some dogs a stern voice is compulsion enough, other dogs may require a stronger form of correction. The definition of compulsion depends upon the dog, his sensitivity and response to the correction not the size of the dog. Now, you are not going to correct a Jack Russell the same as a German Shepherd, the Jack Russell may need a harder correction because it is mentally tougher and less sensitive than the big German Shepherd! Size does not quantify the toughness of a dog. I’ve seen many small dogs take harder corrections than dogs that are four times their size.
It is not cute when a small breed acts aggressively, yes, they may not cause as much damage as a larger breed but they still can traumatize a child or cause you stress.