My first reactions to Lilith's Brood:
1) Heriarchy is not a genetic trait.
2) The Oankali (especially Ooloi) manipulation of humans is immoral.
3) The Oankali are no more moral than humanity, since both are driven by supposedly inescapable genetic tendencies.
1) Hierarchical behavior is too complex to be purely genetic. Unless Butler can point to specific evolutionary pressures that would cause such a trait to occur, I'm going to have to call bullshit on that whole idea. Without that specifically ingrained trait, there is no reason for the Oankali to render all humans sterile (until Jodahs) without an Ooloi. Without that trait human behavior could simply be re-trained. The Ooloi are spectacularly effective manipulators, after all. (I'll ignore the biological impossibility of heirarchical behavior being genetically inherited in my subsequent points, and instead examine morality in Butler's universe, where this is true) And that brings me to my second point:
2) Despite the supposed genetic predisposition of the Ooloi to find new things, to heal them, and to bring them in line with their own idea of morality, I think that their extended manipulation of humans is morally suspect. The Oankali as a race, and the Ooloi in general, do not treat humans as if they have any level of choice, and simply manipulate them. They assume that the humans do not have choice because of their biological contradiction, and the Oankali assume they must choose for Humanity. The way that Nikanj uses Lilith, using it's own pheromones to bind her tightly to it, without telling her about the side effects (She can't touch Joseph), is presumptuous to the extreme and, I believe, morally wrong. Even worse is Jodahs' unwillingness to tell his soon-to-be mates the same facts, despite seeing how hard it is for his human mother, Lilith, to deal with what Nikanj did to her. He assumes he knows what's best, he assumes it will be OK, but really all it is is biological greed driving him. Which brings me to my third point:
3) Here's the Oankali Contradiction: They believe they have the right and the ability to choose for humanity, because humanity is biologically flawed, and the Oankali can "correct" that. But the Oankali themselves are driven by an immensely powerful biological need, that manifests itself in a particular set of morals. These morals are thus no more pressing, no more valid than the supposed lack of morals that the humans exhibit. Both are driven by biology, in this world, and so what we see in the end is a triumph of Oankali biology over human biology, instead of the morally righteous triumph of an angelic race.