I agree that the point was to have a sentient race that logic games could be played with. But I don't think that lets Clarke off the hook for the brainwashing question. Leaving aside that I consider "human nature"to be a very diffuse category (Peru much any attempt to define it narrowly runs into the "all those people over there are "malfunctioning"), freedom of choice alows people to choose whether or not to obey imperatives. In that case, if people can choose not to eat meat, or not to have sex, then can over really call human nature innate? If we could force humans to obey rigid sets if directives, would calling them "natural" and "innate" be any less unethical?

And as far as "limited beings" being created with innate comments, well what if, through neural engineering we could create humans who have "Three Laws" equivalents from birth. Would that be any different from an ethics perspective?