Regarding your encounter on the nudist camp, I understand the person who came and tell you that you couldn't take pictures in a nudist camp. That's very easy to understand on a let's say "moral" ground.
Although one might wonder if the place was a public one, a private one etc. and could challenge maybe the injunction on juridical ground, one might expect people don't want naked photographs of them freely circulating.
I understand you were not taking pictures of people, but the "warden", or the other persons on the place, might not feel like being on a surveillance duty specifically on you to see where you turn your camera. It certainly is something that make people feel uncomfortable that there is a guy with a camera, regardless of where he's actually pointing it.
Some people doing street photography, you know, do exactly this, point the camera first somewhere else, and then on the intended subject.
* As I like saying: "I'm not anti-feminist. I'm misogynous". :)
Regardless of what copyright law states, it has no bearing on the act of photographing, or the act of possessing photos of a copyrighted thing. You cannot legally stop someone from taking pictures of a copyrighted thing if the thing is in the public view. They are two separate issues. Photographing is separate from the act of reproducing and/or distributing. Fundamental ("Constitutional") law governs the former, and copyright law governs the latter. Something must actually be reproduced – that is printed and/or distributed/published – to be in violation of a copyright; thus citing a copyright as justification to bar someone from photographing shows a misunderstanding of what a copyright actually is. You cannot go after someone for a "copyright" violation unless they have actually "copied" something. You cannot bust someone for something you think they might do; you can only bust them for something they have done.
A single unit is a reproduction (or a "print" in photographic terms). The number of copies made does not define something as a reproduction or not; number of copies is related to distribution, not reproduction.
Copyright only prohibits certain kinds of publication of derivative works.
You are free to make as many photos of an object (or objet d'art or artwork including a painting or even another photographer's photos) as you like, but not necessarily free to publish it wherever you like.
A work such as a photograph is copyright the instant it is created, which is when the shutter is clicked. That includes any derivative works made by the same author from it, such as scans or files or prints or silver gelatin prints, etc.
Exactly and to bring it back to buildings, for e.g., you are free to photograph every McDonalds restaurant exterior you wish. But you can't sell a coffee table book called "My Tour Across America Documenting McDonalds' Restaurants". The logo and brand name are trademarked and therefore you would need consent from McDonalds. I think it gets more complex when logo's and/or trademarks become centerstage as opposed to say a cityscape with a golden arch way in the background and the intent if the book is to document skylines or something benign.
"if you want privacy, stay at home" -that is gold. I think people would be surprised at how much privacy they give up in NYC from surveillance video as opposed to the average street shot.
Way to stand your ground. You weren't doing anything wrong.
Copyright protects the work of invention and its author from copying.
Trademarks protect the identity of a business or product. Something different (not copied) but which uses the "identity" of another product to sell.
You can publish a book devoted solely to McDonalds restaurant, and it would not infringe copyright nor trademark, it's a book of photographs, there is no "copy" and there is no attempt to steal identity of the McDonald's franchise.
You can't open a fast food and adopt a similar brand, or logo, in such a way that it could create confusion between McDonald's and your business.
When Andy Warhol used Coca-Cola bottles, or logo, or Campbell soup cans, or logo, in his body of work he was not violating trademarks, nor copyrights.
Certain stock agencies do exclude images having trademarks just because they understand that their typical users don't know the laws about trademarks and would find a way to violate it, and then it could be argued that it was the duty of the agency to educate the client/user, hence the "paranoia" of certain agencies, and of certain photographers, about trademarks, copyright, property etc.
It's all much simpler and, to simplify, it's basically always fair game unless there is commercial use (promotion of a good or service) or defamation (of a person, even a paid model, and of a firm).