Calling anyone in the Middle East cultures a dog especially in Bible times is an insult, kind of like bitch is a sexual insult towards women. I have never seen a strict muslim have a pet dog. Somehow i think theres a message there, in how the culture perceives dogs the animal. I could be wrong, and i would be interested, but muslims tend to go for other types of animals as pets, just never dogs.
So when you read the scripture, its really a depressing terrible way to treat and speak to someone. We have other very bad insulting words, and they hurt, we just dont appreciate what "dog" meant. the scripture is not a reference to warm and cuddly dogs, far from it.