Dogs Are Confusing

I find dogs to be a curious subject. They are simultaneously beloved and besmirched. Dogs are "man's best friend". We name them King (Rex) and Faithful (Fido). They aren't even our pets so much as they are our companions. And yet, to associate a person to a dog is a high level insult. Calling somebody a dog ("all men are dogs"), a cur, a bitch (female dog), or any other term for dogs is deeply insulting. So what is it about dogs? Why do people love them and hate them? How they be both the height of perfection and the most vile of beasts?