"Good neighbourhood" = Ask your child to only use Facebook. Don't let him go near the train station. Leave the Google Safe Search by default. Let them use a video player, but download the content yourself.
"Signs all over the place": I don't remember seeing the sign "Warning: Guy selling drugs here" in the backstreet next to my town hall (Lyon, France, not a small city), nor the "Beware of aholes" sign in my highschool ;) and I especially remember 3x4m panels of ads for dating Minitel site (in France) with the curve of a woman's back: The bad world has never really been separated from children, but we'd teach them. I would teach my child to not click on ads, blinking stuff and bodies if they still meet any. They'll have to resist when the hormons kick in, so they'd better learn young.
Then, monitor him/her/ah. It's not normal, for a child, to sit unsupervised at a computer for more than a few minutes. Place the computer in the living room, not in their room. They exactly know what to do and where not to click when the parents are around ;)
Which means: Problem solved. Yes, some may fall addicted to porn or see curse words, but only if parents don't spend enough time to supervise them, pretty much like in my youth. But at least, other citizen remain untracked.
Perhaps the best way to think of the problem is like this: Yes, kids having access to porn and NSFL content is potentially damaging to society.
However, a society where the state keeps a detailed record of everyone's personal sexual preferences is potentially even worse off.
A thought just popped up in my head about this. Yes, the internet is a reflection of the physical world, but it doesn't have any of the constraints that we have put in the real world. In the real world, you try and select a good neighborhood to raise your children in. This saves them from even coming close to physical spaces we'd like them to avoid.
Then in the real world you have signs all over the place that warn you from entering a dangerous situation. Then we regulate access to some of the more dangerous places (places that deal with hazardous materials, prisons, etc). You have things like the "Sex offender registry" which warns you of people to look out for. You have a lot of safeguards in the physical world that nobody bats an eye at because they all make sense.
And on top of all this evolution has given you an innate sense of danger. So you naturally stay away from people with knifes, guns, etc.
The internet has none of this. So while I'm all for freedom of information, I still think there is a need for some protection. On the internet, adults and kids are some of the time just 1 click away from a NSFL site, except of course that kids can't recognize that; which might be true for some adults as well.