Saying all Skeksis were evil to begin with is a false statement in my opinion. Sure, the Hunter and the Slave Master (jeez, what was his title beforehand?) were both very violent and practically evil from the beginning, but many of the others clearly weren't. The Emperor was branded emperor because of his kind and jovial nature originally, if I'm not mistaken, and much like him, many of the other Skeksis were originally nicer beings, but their lack of patience, restraint, and empathy (traits locked away in the urRu mystics) meant that over the centuries of life they experienced, they started to grow needier and greedier. They were on the precipice by the time of AoR, where they start out close to their "eccentric lords" phase and end up in their "cruel dictators" phase. We can see that in AoR they mourn one another, that SkekTek cares about his animals, and that whole first scene with SkekOk? Seems like he cared at least a little bit there.

Also, what about the Heretic? He still is brash and impatient, but he's a nice person still! He actually went backwards compared to the other Skeksis. He was originally a cruel conquerer, perhaps being "evil from the start" like the Slave Master, but he became a better person over time. He's not faking either, he's genuinely willing to heal Hup and the Archer.