The reason why Ben could not kill Penny when he saw she had a child was the same reason why he could not kill Danielle when he saw that she had a child: Ben's own mother died giving birth to Ben. Ben may be able to kill a random person if it suits his or the island's purposes, but if he sees a woman as a mother, and realizes that he would be putting that child through the same motherless life he lived through. He is unable to inflict the suffering he felt from not having a mother his whole life onto another innocent child. Evidence: Ben was fully prepared to kill Penny until the moment he saw little Charlie and realized she was a mother. To claim that he coincidentally had an epiphany about (insert first theory, above, here) would diminish the intentional impact the writers made of Ben see