I think it's wrong to view that behavior from dogs as motivated by love. They are programmed to be a part of a pack structure, and alpha males don't achieve their position with affection. Of course, dogs can feel affection for an owner, but their loyalty to an owner isn't necessarily based in affection. We see unconditional love, but it is an instinctive behavior.
IMO if you view the behavior of dogs in this way, their behavior starts to make more sense, and is more predictable. People often talk about dogs being nice or mean, but often their behavior in a certain circumstance can be predicted by their environment. For example, a dog on a tether feels extremely vulnerable, and will act very differently based on whether or not its alpha is present. A mistake I often see people make is trying to pet a dog by extending their hand over the dog's head. This is usually ok if their alpha is present and the person has interacted with the alpha in front of the dog, but if the person has just walked up or if the alpha isn't present, the hand over the head is seen as a challenge for dominance, and the dog is more likely to bite.