Bob, I think you did a much better job answering Jenn's question. Mine was more of a clinical dissertation attempting to explain people's opposition to child nudity- and perhaps even implying agreement with it- which is not the case. On the contrary, I think as your cousin found out- there are times when nudity just makes good sense. Swimming and sleeping are such times and I'm glad that your mom had some success having Auntie see this point.
So to put my reply in more personal terms- which I think is what Jenn is looking for- my wife and I were products of the rebellious 1960s. While we weren't exactly hippies we did agree with many of their ideals- one being that there was nothing shameful about the human body and no reason to act as if there was. I too began sleeping nude as a early teen- soon after I began experimenting with "going commando"- or freeballing as we call it now. I had been wearing my UW to bed but it seem dumb to put on UW just to go to bed. When I met my wife to be she quickly adopted my buff sleeping style as well my casual attitude towards nudity. We even visited a nude beach on several occasions.
After we married we built a house in a secluded area of southwest Florida. Because it was hot- and secluded- we treated clothing as largely optional- especially in and around our pool. This included the kids as they came along- no one wanted the hassle of bathing suits- and clothing was pretty much optional any time we didn't have visitors- which wasn't often in those days.
In fact, about the only visitors we had was my wife's brother's family who would drive over from Delray a few times a year. They had two boys and a girl. Her brother's wife was very conservative and didn't go for this nude swimming and sleeping so I told our kids it would be best if they wore swimsuits and sleep-shorts while their cousins were here.
Perhaps I gave in to easy but I knew as they grew older- made friends, had sleepovers, joined scouts- went camping and so-forth that this nudity question would come up over and over and it seem best to adjust them to the idea that you make certain accommodations when around guests and one of those is to wear clothes when you might not otherwise. They accept this and I think it even made them appreciate when they could be clothesfree even more.
They are long grown now- successful well-adjusted adults and I've never seen the slightest sign that their clothes optional upbringing had any adverse effect on them.