The only thing that has changed is the ability to openly talk about sex. When movies first started out, there were plenty of movies made that would get an XXX rating now. Ratings systems were founded that had puritanical rules regarding language, violence, and nudity.
TV regulation was much the same. Think back to shows from the 50s and 60s where they showed married couples sleeping in separate beds.
I've had this same talk countless times with a few family members, but my argument is always the same: the only thing that's changed is how much TV imitates reality, not the other way around. People were having premarital sex well before TV, TV has just become more realistic about it. I think that we're better served by the changes over the years because now we're seeing situations on TV that may mirror some situation that we've been in or will be in. This openness about sex and other formerly taboo topics makes it easier for us to be open about and willing to deal with topics that everyone knew existed, but were not allowed to speak about openly.