As you all know tobirama talked to sasuke about the uchiha being a clan possesed by evil perhaps that was a bit too much. But they do seem to be cursed by hatred. With itachi or shisui seeming to be an exception. The fact is i dont believe either of them were immune to it. Itachi killed his whole clan to protect the village and never fell into darkness even when surronded by it. But we must remember itachi did not lose the person he cared for most. Yes it was shisui's death that awakened his MS buy imagine if sasuke was killed by danzo or hiruzen failed to protect him. He was willing to betray the leaf by leaking info if sasuke was harmed but i believe he would have fell into darkness if and turned out like madara if that happened. Even someone as pure as obuto was turned when the person he cared for most was killed