I'm sure that there are many people who agree with him on points one and two. It's when you get beyond there... (But there's a certain logic, in that if you want to make sure that what you're calling "art music" can be absolutely, clearly one hundred percent differentiated from pop, and with good reason you don't trust standard usage to do this, you have to get rid of any possible hybrids - he'll sacrifice any number of babies to get rid of the bathwater. This is one of my favorites (in his def'n of art music): "It must be written for acoustic instruments and/or unamplified voices (Mechanical and electr(on)ic devices may be employed for textural effect, but not as the main 'instrument'. Technical amplification, for recording purposes or to enhance performances in arenas of poor acoustics, are not part of the composer's effects or intention, and are not counted.)")

My impression from Josh's email was that this was a recent discovery, though actually looking at the email now, Josh doesn't imply this one way or another. He does say, "The amount of helpless resentment on display here is impressive."