Using Bad Recording to Evaluate a System

Once I went to a dealer to audition a speaker, brought a few CD's. One of them was a CD of a group I like but has rather low quality recording.
Well, I put that CD in and cued up a track, and when the music ended the dealer asked why I was using such a horrible sounding recording to audition. (I think he looked kinda slightly pissed. Maybe because the music sounded shrill and irritating the whole time???)
Yeah, why?
Here's what I think: an audio system should make listening the music a pleasant experience. The better your system can reproduce, the more enjoyment you get regardless of recording quality. Saying that 'my system is so good I can only play my audiophile discs' is basically saying something is wrong with my system. Yes, nowadays I tend to play my 'audiophile' CDs much more than regular ones, but that's because of the music AND the excellent recording quality, but when I play my regular or lower recording quality CD's, I find that, although the shortcomings are more obvious, my system can reproduce the music as an enjoyable presentation, and I enjoy it more than when I used to in prev. lower-res/quality/musicality systems.