We are programmed to find sex pleasurable for one simple reason—because animals who mate have offspring. Those who do not mate have none. Traits that result in successful reproduction get reinforced and passed on. Evolution is that simple.
It is therefore useless to bemoan as evil the fact that men tend toward aggression. Among our ancestors, aggression often helped males have more offspring than their competitors. “Good†and “evil†had little to do with it.
That is, until we reached consciousness, at which point, good and evil became pertinent indeed! Behaviors which might be excusable in dumb beasts can seem perverted, criminal, when performed by thinking beings. Just because a trait is “natural†does not oblige us to keep it.
David Brin