Lmbrghini: that's an interesting reference you provided. Thank you.
What I gather it says is that the FAA has general guidelines, but the application/operationalization of those differes from one airport/airline to another. In other words, travellers can have no confidence at all that what they are carrying won't violate the (unposted) rules at a given airport. even within an airport, the application differs--it happened that the incident I started this thread with took place at the very same security checkthrough I had been through about an hour earlier (went back out through security into the main terminal for some food). So, that's an example of the same people (recognized them from the earlier checkthrough), same shift, looking at things differently depending on which individual looked at my possessions.

So, I guess what we have at the more detailed levels of what's dangerous or not is confiscation by whimsy (and, unfortunately, the Whimsies are a very large family).

I would guess that inconsistent applications of this sort are the basic building blocks of legal action, but that's not my area, so I can't say for sure. The lack of posted regulations seem to me to be pretty problematic.