Rape probably wasnt risky during caveman days.. or i should say, far far less risky. IF your stronger than the woman, without a society whats the risk? Only risk is the woman might kill you, which is a valid risk, but presumably minimal if the man is stronger (or with a group).
Perhaps thats the issue, we evolved that trait back when the risk was low and now that the risk is high our evolution hasnt fully caught up.