As an example of a valid justification, suppose a king in the Middle Ages wanted to maximize male baby production so he could have the biggest armies. He might well set social incentives for baby production both through marriage and out of marriage sex, and set negative social incentives for gay behavior.
Right. The king would need to breed a lot of women so that he would have a lot of women to breed a lot of warriors from. By then he would be too old to be king any longer... if he hadn't already died from old age.
