I wish I could find it, but I can't: I read (I think it was blog) of a famous writer, who heard for the umpteenth time the phrase "Oh, I thought I'd write a book"* at a dinner party and the 'put down' was incredibly polite, and incredibly intelligent and very funny as he listed all the things he, the writer had done, in the five years it took to become published. IIRC he spoke over the dinner party guest at least five times as they started to say "yes, but..."
I liked Neil's response.
*But I did love it when, in a similar response, the Beatles met Ken Dodd, and Diddy said he was thinking of forming a group, and wanted to think of a good down-to-earth name for them. "How about the sods?" John Lennon asked.