You
really need to answer questions directly as asked, and not whatever question it is you think the other person is asking. Doing this only creates confusion. There are many occasions where I see this kind of miscommunication happening between users on this site without either person realizing it.
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.