Data and Lore

In TNG, Data and Lore are identical twin android "brothers." Yet Lore is Data's alter ego. Data is good, while Lore is evil. Data is the Boy Scout to Lore's serial killer. 

What makes one good and the other evil? Simply that Lore was wired a little differently than Data. Lore was a failed experiment. A defective model. Noonian Soong was learning by trial and error how to make an artificially intelligent robot. 

Another example is The Terminator series. In the first film, the Terminator was programmed to neutralize John Connor. In the second film, he was reprogrammed to protect John Connor. 

From a secular perspective, that's what morality comes down to. It all depends on adding or removing something from the brain. If natural selection installs a morality chip, that makes you "good." If the chip is removed, that makes you amoral. If the wrong chip is accidentally inserted, that makes you "bad."

Morality is arbitrary. It's all about parts. Reducible to parts of the brain. If you replace one part with another part, you replace one morality with a different morality. Data and Lore are different because their circuitry is a bit different.