there are a lot of negative aspects of sex - unwanted children, abortion, disease, if a woman has a STD and gets pregnant, the baby also gets the disease, heartache, negative emotions and mistrust, dislike of the opoosite sex, prostitution. It can create a user society where everyone uses other people. Also a bad reputation. Could even lead to sucide or murder if a loved one cheats. Divorce, broken families.
Common sense would tell people to avoid this. I agree with the person who stated it is about emotions, social acceptance.