There's nothing pernicious about this analogy.

NYM

We've all seen videos of violent attacks in public places, in which bystanders, bystand. These are metaphoric sheep. They are incapable of violence, even as the empathize with victims being victimized. 

In nature, there is no moral component to wolves wanting to eat sheep. From the standpoint of sheep, wolves are terrifying monsters.  People who prey on other people, may be thought of as metaphoric wolves.  To the extent that people are sheep, the wolves can prey without risk.

Some people look just like other people, they have empathy for their fellow person but are also capable of violence.  These are metaphoric sheepdogs.  Sheepdogs often look a lot like sheep, with long fluffy fur--perhaps this was so that the sheep and the sheepdog would bond, or to prevent the sheep from being afraid of their guardians.  Maybe it was a way to make it harder for predators to tell from a distance if there was a guard dog around.  In whatever case, when the flock is attacked, unlike actual sheep, the sheepdog goes full-on dog and springs into action to protect the flock.