I tried finding info in this area, but the only half black flags I can find of a political nature are half black half red for anarcho syndicalism, and half black half yellow for anarcho capitalism (but you probably already knew that).
Apparently, this is used in racing
https://en.wikipedia.org/wiki/Racing_fl ... white_flagA diagonally divided black-and-white flag is displayed with a car number to indicate a penalty for unsportsmanlike conduct. This flag can be displayed if a car tries to intentionally drive another car off the course, or if a driver gets out of his/her car and initiates an altercation with another driver.
Some administrators (NASCAR and IndyCar) do not distinguish mechanical problems or unsportsmanlike conduct from rules violations and simply use the solid black flag for all violations.
Edit: Ahh, Anarcho-Pacifism
But all the same, I picked it up in a military surplus store, and there were a ton of them. I feel like there's a more mainstream interpretation.