No it is because animals are helpless, humans are not.
Babies are helpless, children are helpless. It pisses me off that people can beat their children by the dam road and when people report it the parents can say they were just chastising them. But when a animal is seen getting punished, the dam SWAT team kicks in your door, blows your brains out, and "liberates" the animal from abusive clutches. This is one fked up world.
On topic, while Serana may be a vampire, vampirism doesnt always change the person. Her parents werent always the crazy power hungry vampires that they are now. According to Serana, they were once loving and caring, but the want for power changed them, as it does many. Thankfully though, its not the case for Serana. Nor for my vampire character, which I should probably pay a little more attention too.