When a colleague told my father that "duplication is always bad" he grabbed a random memo from that colleague's desk and said "I bet there's at least 3 copies of this piece of paper in this building". That drove the point home alright.
I think the riposte is against the word "always" and it worked precisely because one could blindly pick a counter example from the physical space of the discussion.
I.e. it worked because it smashed the broad statement and forced a discussion about particulars. Now who was right about those, I have no idea, since I wasn't even present.
