The first thing that comes to mind is something my grandpa told me. "Never get into an argument with an idiot. People walking by might not be able to tell the difference."
That being said his statement may be true in his frame of reference. If you take 10 guys give them shitty Red dot sights and no training on how to use them they will probably prefer iron sights.
If you give the same 10 guys aimpoints and show them how to properly use them the outcome will of course be very different.
I have never met this guy but he is probably one of those old school, "I used to assault the communist hordes at Chosin"(loosely stolen from Buck) types. Your not going to prove him wrong with science. If you still want to prove to him what you already know, the best way to do it is on the range with a shot timer.
I have had many a student think their way was the only way until I put them on the clock and show them a more efficient and subsequently faster way technique.
Just my 2 cents