He's a dinosaur, stuck in the 70's forever
RE: "its much easier to control a dynamic transducer with an open back" - I agree and if I recall correctly, that's an infinite baffle, and even the t-rex should know that makes for a lower bass extension and less sound coloration than from a driver in an enclosure (although those enclosure effects can be mnimalized or turned into an advantage in some cases, it is usually a trade off somewhere).
Based on his opinion of electrostatics, I had to wipe out the idea in my head that he was a Magnepan speaker and moving coil LP cartridge kinda guy. Those things will still sound great in today's world, like they did 25 years ago. But it's the bigger issue that drives me nuts - of the people who just never move on, get stuck in a time capsule, and miss out on a lot of new stuff. Even worse, is they don't even try to get the education about what is going on today to talk intelligently about it.
One issue he beat you up on was the "true sound" - he just couldn't explain that what he meant about "has to travel through air" was that it has to "interact with the outer ear."
If the recording is supposed to sound right to people, they have to experience it in all the phase corectness of interacting with the outer ear/pinna. The way I see it, music mixed by a sound engineer using a custom IEM will sound different than the same music mixed using headphones, because the headphones will add in some spacial timing issues reflections that were not available to the IEM user. Music mixed with monitor speakers or headphones is going to please the speaker and headphone listeners better than the IEM people. We complain all the time about losing sound stage with IEM's - and there is a reason.