DISCLAIMER: I am also a childless libertarian. I don't actually plan on ever having kids. However, my hubby and I do discuss what we think about censorship, spanking, grounding, etc., so I have thought about this.
I want my kids to read everything they can get their hands on. I think TV and movies are a different matter, though. With books, the kid has to imagine. If they don't have the images or concepts for the words in the book, they just won't understand it. With TV and movies, it doesn't matter if they don't have the images--someone's giving them to them. That can be horribly traumatic for kids. At the same time, I don't want to have to hide our horror movies or Buffy or Angel DVDs--cause that just means they're forbidden and the kids will go looking for them and watch them alone, which in my opinion is worse than watching them with my knowledge. If they really think they're ready for adult content (and I think they're ready for adult content) I want to watch it with them so I can explain things that they might feel uncomfortable with. That way, I'M raising them, not the TV.
That said, my hubby and I were raised in extremely different environments, and I think the above plan is kind of the best of both worlds. My parents wouldn't let me watch anything above PG-13 until I was 21 (though once I turned 18, I went to R movies ANYWAY, cause who did they think they were?). They weren't happy with me watching Buffy (it started when I was 16, but I didn't really get into it until I was 18), but didn't really stop me (although watching Buffy and Angel getting it on with my dad in the room was one of the most uncomfortable experiences of my life). My hubby, on the other hand, was given carte blanche to watch pretty much anything he wanted. As a kid, he saw Hellraiser, most of the zombie movies available, Stephen King movies, the Alien and Predator movies, etc. etc.--stuff my parents would have freaked out about. Both of us turned out okay, I think, though when I left my family and got out into the real world, I was kind of culture shocked, while my hubby's fine with anything life throws at him. Of course, his IQ is remarkable, so I think he had the capacity to process those things and understand the difference between fiction and reality at that age. I don't know that most other kids are able to do that.
So that's my $.02.