Dave,
You make a very interesting point. I agree with you that parental responsibility is paramount, and raising your kids properly from an early age goes a long way toward making it easier to deal with these kinds of issues. My concerns are, though:
1) There's nothing about pen turning that makes it a truly adult interest. I can see kids 10-plus years old being interested in pen turning, and being very good at it. Much like sports and music, it is the kind of activity at which I would expect a kid to be able to excel, because when you're able to focus on it and practice, you get better at it. If it's not a purley-adult interest, unless we want to make the forums adults-only (which we basically are anyway at this point, although our terms of use say 13+), I don't think it proper to focus on the art/craft/whatever you want to call it, and our conversations (even those tangential to the topic) as being inherently adult-only.
2) Of course, this doesn't mean that I'm for closing CC, or even censoring it to any significant degree. Yes, sometimes potentially offensive or inappropriate things are posted. In most cases, I do what most people do and simply close that topic, but in some cases I can understand why some people might be offended. An accurate subject line that warns potentially sensitive readers about the content goes a long way toward mitigating the need for censorship.
3) While the level of discussion gets rather heated some times, one of the great things here is that we don't usually split into two camps and fight simply to fight. Instead, we tend to talk things through, with the majority of the people trying to find a common ground between any divisiveness. Sometimes, both sides merely have to agree to disagree. I actually think that the lesson in that is a good one for kids to learn. I don't know that I want my kids exposed to EVERYTHING that gets said, but the ultimate outcome is a good one, and can help supplement the lessons parents teach their children.
So, my vote is to keep CC open too.