why the sillyness.?

[HFat]

Most Americans don’t think this is the function of the government, and that it should be left to parents and/or private institutions (theaters, retailers, etc who voluntarily want to enforce the ratings).

And that's only part of the issue. If the government is going to censor movies, why should it empower an industry organization that's not acting in the public interest to do that?
Organizations like the MPAA go after unaffiliated productions and the cultural expression of minorities the world over. If you care about free speech, art or diversity, you don't want to make the distribution of unrated content illegal in any way! The tech to make movies is getting cheaper and cheaper and compulsory ratings are therefore becoming more and more of an hindrance. Should the stuff that hasn't got a big budget or insider backing be shown only on computer displays? This goes way beyond what's appropriate for children.

is not easy to reliably prevent minors from viewing inappropriate sites

It's very easy with default-deny and lots of people are working on default-allow products (which are much harder to get right and never perfect), including governments. Obviously the same tech can be used for censorship so there's lots of money to be made in that area. People tend to balk at default-deny (laziness?) but the Internet as a whole isn't appropriate for young children. It ain't just the porn.

[m0002a]

It's very easy with default-deny and lots of people are working on default-allow products (which are much harder to get right and never perfect), including governments. Obviously the same tech can be used for censorship so there's lots of money to be made in that area. People tend to balk at default-deny (laziness?) but the Internet as a whole isn't appropriate for young children. It ain't just the porn.

Any half-way intelligent 12 year old kid can overcome whatever Internet site blocking settings that are specified. At worst (and not that hard to do) is that they can find an old computer laying around and install Windows or Linux from scratch without any child protection, and connect to the network. A group of kids only needs to find one such computer in the entire neighborhood, and they don't have to be encumbered by what their own parents do.

[HFat]

You ideally want the software on a router of course. That's the only sane place to put it really.
If you're going to run software on hosts, then don't let any host connect to the network with full priviledges. That's not very hard to grasp I would think. And that's how people normally set up networks they want to restrict access to.
12 yo children can not bypass basic security. They can only bypass snake-oil security. You can't expect any parent to know something about information security but I think you can expect them to ask someone who has a clue. Like when they see a doctor about their kids' health instead of playing experts.

But yeah, anything can happen if children are entrusted to untrustworthy neighbours, friends, family members and so on. That's basic, right? Yet so many peole fail at this. An unemcumbered Internet connection ain't the worse thing that could happen... not by a long shot.

[alleycat]

when you say "nudism" do you mean that as it is now commonly ment (public nuditiy in an area restricted to people who are all nude, e.g. nudist beaches and holiday camps), or simply not covering up totally and all of the time whilst at home.?

Both, although my parents weren't nudists as such; we were invited to a holiday camp a couple of times by friends of the family.

did you get the following from Richard Dawkins book "The God Delusion", it sounds very familiar.

I'm aware that Richard Dawkins coined the term "meme" in his book The Selfish Gene, although I have read neither it nor The God Delusion. He's obviously a clever bloke, but from the little I've seen of him on TV, he comes across as rather arrogant, almost like a religious zealot funnily enough. The idea I expressed came from my own personal reflection, but I'm sure that I'm not the only one to reach this conclusion.