In this case I asked a yes or no question because I simply wanted to clarify and understand the nuance of your position. You shouldn't always assume that every person responding to your comments is immediately trying to argue against you (although I'll admit this a fairly accurate heuristic for internet discussions in general).
Instead of answering with "Yes, (I believe) it is impossible" or "No, it is possible", you answered with the following:
"You can always present a case history of one".
Because I asked you a yes/no question, I am going to interpret your response as a framing of a yes/no answer. I interpreted your comment as: "(No), you (one) can always present a case history of one".
Hence my confusion: it sounded like you were holding both beliefs simultaneously: "Yes, natural monopolies are impossible, but there are counterexamples".
In the future please just answer the questions as they are asked.