Eh, animal comparisons can be fun and poetic and all that, but it runs a little heavy into the essentialism and sometimes overruns important lessons in human nature.

That there's very little coming back from the extremes that most people would consider evil/tyrannical is true (wolves stay wolves as you say), for some it's so strongly inherent that the born different implication of "wolf" fits, although that's more the serial killer archetype. For the power elites willing to inflict undue suffering on millions at a whim, that's generally as much learned/trained lack of empathy as it is inherent, but humans are terrible at unlearning so there's little hope of them ever rekindling any care for their fellow man, it's far more likely that only being overpowered will stop them hurting others at that point.

The point being that wolves Vs sheep conjures an image of inherent incompatibility that when you look at the individuals in question may be obviously false. When you come face to face with them it's important to be sure in advance of your convictions that even though they're actually the kind of person that in a different world with a different past could have been a good friend, the things they have learned and done have made them incompatible and there's almost no going back now.

Because they sure as shit already think you're beneath humane consideration and won't hesitate to do what needs to be done, they wouldn't be in power if they did.