When it comes to dog attacks, especially at places like dog parks, people blame the dog that attacks first. This is often very mistaken. Rarely does a dog attack another dog without reason, unless it's a red-zone case of dog-aggression, in which case such a dog should not be at a dog park. But 9 times out of 10, the dog being attacked instigated it.
Many owners are completely unaware of the signals their "little angel" sends to other dogs. It's amazing how few owners understand and interpret dominating posture and behavior in their own dogs. Jumping up on you when you come home from work, can be a dominant behavior. As can "asking" to be petted. Many subtle dominant behavior are overlooked, especially in small dogs, because they are "cute"
However, when left uncorrected these behaviors can get the dog in trouble in social settings with other dogs.