Things are actually headed in a better direction morally. We now have way better view points on thing like rape, racism, abuse, murder and violence in general. Polygamy is old (hella old) and is even permitted in Abrahamic religions (old testament multiple wives and ditto for islam), incest is almost universally taboo (except for on reddit). Marijauna is only a cultural taboo imposed by wack job puritans and racists and is no more morally wrong than alcohol. Prostitution is complicated and really depends how it is conducted. Sex slavery and pimp controlled hooking is obviously wrong, but I don't see anything wrong with it being voluntary and regulated.
Check the link below. (note to Admins: it's not really porn please don't ban me!)