good parsing, firsty
I think you are correct in pointing out the fallacy in lovey's argument, namely that sex and pornography are not interchangeable.
however, I tend to agree with lovey that if you want to watch porn on your car tv (if you are a passenger and not the driver) or on your front porch giant screen that should be up to you.
The solution to the problem that you fear--exposure of innocent child-eyes to unsavory sights--is not restriction but openess.
We need to teach our children not only about sex but about pornography--arm them with information.
They are going to see pornography at some point unless they are deaf, dumb and blind. It's out there and it isn't going away. In my opinion porn is used in advertising directed at the very kids you are talking about.
Tell them about it. Show it to them. Explain it to them. Desensitize them to it.
Otherwise I suggest that you move somewhere like a fundamentalist moslem country--they deal with it by covering it up.