None of those things need to happen, social advance in education and scientific education in medicine will do alot towards getting rid of them. Most of us who have had sexual partners have neither contracted STDs nor have unwanted children.
Okay, now on to my bonus points. Morality has nothing to do with
religion. As Clyde even said, the only thing that matters when it
comes to morality is whether or not people are harmed. So, is
society harmed as a result of a significant percentage of the
population having multiple sexual partners? Of course it is.
There are the STDs, the unwanted pregancies/abortions,the single-
parent children. All of these have negative effects on individuals, as
well as society; and each of these are increased as people have
more and more sexual partners. There, I win... even more.