As for your situation, Steve, I think I would have gone off the deep end myself. You handled it rather well, I think. With someone coming up to me with automatic weapons outside of a military installation it's more of 'yes sir, no sir, type of reaction and getting my butt out of there. Not gonna argue with a man or woman with an automatic weapon or a weapon of any sort. However, someone in a public area telling me to stop doing something where no sign prohibiting said something (taking pictures) would be a different matter entirely. I would have called her out on it, courteously of course, but called her out nonetheless.
On my trip out west last year, I can't tell you how many pictures were took at rest areas. No one stopped me from doing that the entire trip.