Vision,
One thing we've already taught our kids is that as long as they live with us and as long as we are paying their way, they will abide by our rules. They know that one day they'll be all grown up and ready to make their own way in the world, have families of their own and then they can make all their own decisions.
Kids have a strong (sometimes overblown) sense of fairness. Both my kids already see that it's more than fair to respect our wishes as long as they are living at home. (And, we've already told them that they are welcome to live at home for as long as they want!)
Whether they like it or not though, we took on the responsibility of raising them, and teaching them values and wisdom. We are honest with them that we sometimes make mistakes and maybe ban something that doesn't need to be, or even allow somethings that we shouldn't of, (like when my son watched an old movie that we all though was fun, but then he had a nightmare) but that we really do love them and are doing the best we can to raise them to be responsible, caring adults. When they have their own kids, they can correct whatever mistakes we made, and go on to make mistakes of their own.
Boanerges; yes, that's exactly my issue with the program. As I mentioned in the OP, can you imagine what the response would have been if "Marsha Brady" became pregnant in "real life". I don't think they would have just gone on as if it were no big deal back then.