Intellectually, he knows that he loves his sister, but his emotional capacity to do so has been removed. Intellectually he knows that he probably still loves Ellesime, but he is not capable of love, and his condition has eaten away even his memories of what it was like to love. He still remembers it as a concept, much like one might remember having learned to ride a bicycle or flying for the first time at some specific point in one's life without actually remembering what it was like.
And with his ability to feel destroyed and his memory of his life as an elf badly deteriorated he has become the monster they punished him for being previously. He didn't set out to be a monster initially, but now that he has become one anyway, why exactly should he not pursue his old goal? Why should he care about torturing some shadow thieves or a couple of bhaalspawn? "The law" means nothing to him and his conscience has been taken away with his soul. What is left for him but to seek power for the sake of power, and maybe settle some scores along the way?
Really great analysis. And there are layers to the story as well. That's the story from Irenicus' positions but we very briefly learn that there is another side to story. Bodhi encouraged his ambitions and he tried to take over the tree to become a god even before the removal of his soul. He's so busy blaming Elliseme and Elean (sp?) for his misery, so convinced that the way to undo the curse is through magical mastery that he's blind to the path Elliseme wanted him to follow, redemption through acts of goodness and compensation.
So he was actually evil before but becomes a very different type of evil after the loss of his soul. Cold, calculating and driven by desire to feel something again.
