Agreed- even defining the notebook as a moleskine suggests a certain type of content. More so, it's a seemingly generalized trademark (like Kleenex or Xerox).
But by questioning why he voiced his argument, you validated his argument and thus the reasoning behind it. Your question, posed as such, answers itself, in a way.
Why do people insist on telling us their pet peeves? It's just your pet peeve dude...