...and to be honest, it is this sort of claim that tends to alienate.
I think of myself as a pretty open minded person. I have dove in the presence of (but not with) DIR/GUE divers and respect their "style" of diving and the committment thereto.
I can't speak for the "anti-DIR" diving community, but truthfully, I am very satisfied with the QUALITY of my diving and I cannot see where/how adopting a new equipment configuration and diving methodology could lend to its improvement.
What DIR would offer me, if I chose to embrace it, would be a change in the NATURE of my diving ...not the QUALITY.
Well, the real problem with his statement is that the term "quality" means different things to different people. His definition of "quality" may (and most likely does) differ from yours.
OTOH, you mention being open minded and diving with DIR divers, but you can't see how adopting a new configuration and diving method would improve your diving.
Is this statement made after actually trying it for yourself over the course of 4-6 dives, or simply from watching/being around them and deciding it doesn't work for you?