Why do intelligent people deny audio differences?

In my years of audiophilia I have crossed swords with my brother many times regarding that which is real, and not real, in terms of differeces heard and imagined.
He holds a Masters Degree in Education, self taught himself regarding computers, enough to become the MIS Director for a school system, and early in life actually self taught himself to arrange music, from existing compositions, yet he denys that any differece exists in the 'sound' of cables--to clarify, he denies that anyone can hear a difference in an ABX comparison.
Recently I mentioned that I was considering buying a new Lexicon, when a friend told me about the Exemplar, a tube modified Dennon CD player of the highest repute, video wise, which is arguably one of the finest sounding players around.
When I told him of this, here was his response:
"Happily I have never heard a CD player with "grainy sound" and, you know me, I would never buy anything that I felt might be potentially degraded by or at least made unnecessarily complex and unreliable by adding tubes."

Here is the rub, when cd players frist came out, I owned a store, and was a vinyl devotee, as that's all there was, and he saw digital as the panacea for great change; "It is perfect, it's simply a perfect transfer, ones and zero's there is no margin for error," or words to that effect.
When I heard the first digital, I was appalled by its sterility and what "I" call 'grainy' sound. Think of the difference in cd now versus circa 1984. He, as you can read above resists the notion that this is a possibility.
We are at constant loggerheads as to what is real and imagined, regarding audio, with him on the 'if it hasn't been measured, there's no difference', side of the equation.
Of course I exaggerate, but just the other day he said, and this is virtually a quote, "Amplifiers above about a thousand dollars don't have ANY qualitative sound differences." Of course at the time I had Halcro sitting in my living room and was properly offended and indignant.
Sibling rivalry? That is the obvious here, but this really 'rubs my rhubarb', as Jack Nicholson said in Batman.
Unless I am delusional, there are gargantual differences, good and bad, in audio gear. Yet he steadfastly sticks to his 'touch it, taste it, feel it' dogma.
Am I losing it or is he just hard headed, (more than me)?
What, other than, "I only buy it for myself," is the answer to people like this? (OR maybe US, me and you other audio sickies out there who spend thousands on minute differences?
Let's hear both sides, and let the mud slinging begin!