This is social activist graffiti at its finest. I am more than used to seeing stop signs with further instructions (Stop Driving, is, I think, my favorite, although I’m still waiting for In the Name of Love) after so many years in Berkeley, but this takes it to a whole new and better level.
Much like the fire danger signs, this new form of graffiti is updatable! No more permanent records of obscure propositions from long enough ago that no one remembers which regressive or repressive issues they were about. No more dead dictators eternally remembered in spray paint!
Best of all: no actual harm to the sign. Your tax dollars are at work, after all, in providing the sign. I am sure that the person raising consciousness in this fashion will remove and recycle the topical portion once victory is achieved.