I wonder if there are more philosophical nudists, or if, like me, people feel we are somehow programmed to be nudists.
The "philosophical nudists" you mentioned generally call themselves naturists, and they'd say that being naked is part of an outlook that involves acceptance of the human body, in all its varieties. You'll need to explain "programmed to be nudists". Take a look at the Naturist Society at http://www.naturistsociety.com/
By programmed, I mean that for some reason, either genetic or conditioned (and remember that complex systems are sensitive to initial conditions, so conditioning doesn't have to have been a big deal), someone wants to be socially nude. Amotillado mentioned the naturists and Naturists. Social nudity goes back a long time, but formal or codified "nudism," what I called "philosophical nudism," goes back to the German lebensreform (life reform) movement of the late nineteenth and early twentieth centuries. It took a guy named Richard Ungewitter's publishing a book called Die Nacktheit -- Nakedness -- to get it on the popular radar. Ungewitter related it to the rest of lebensreform -- vegetarianism, health, socialism, and so on -- in fact made it central. There's more, but the idea remains that social nudity is a good and necessary thing, because it reconciles us with who/what we really are. I buy all that, but I'm really a programmed nudist. I'm deeply moved to be naked -- by myself or in a group.