Great question Say811, and great callsign SwampWalker.
Most high-end audio enthusiasts prefer no tone controls, which I buy into up to a point. I think that that argument works exept when you talk about the very deepest bass. From 20Hz-200Hz the room and speaker placement affect the freq response +/- 25%. I have a unit that has a sound pressure mic and meter. It has an EQ that allows me to adjust the bass with 6 sliders from 22.5Hz to 125Hz. This allows me to carefully correct deficiencies in the speaker output and its interaction with the room.
Having said all that, I prefer no tonal adjustment. My tone controls are set to flat (can't be defeated unfort.). Also, I adjusted the speaker placement without using any tonal adjustment. In the end, all I have done is boost the freq at 22.5Hz and 32Hz.
As you have noted, this adjustment would offend some, but to me that small adjustment adds the extra foundation my system needs.
Now to the second question that was raised. How do we evaluate systems, by their specs or with our ears? And do cables make any difference at all?
Don't we end up using our ears in the final analysis? Our ears are very capable discerners.
I would rather have a "musical" experience rather than a technically accurate one. I have made three changes to my system in the last two months. Each one has occurred with a two week separation, so I can pick out the changes.
1) I replaced my old copper (read oxidized copper) speaker cables with inexpensive twisted pair copper cables until I figure out what speaker cable I want. The sound is much brighter. I'm not saying I'm satisfied, but the change was big enough for my wife to say, "What's wrong with the system."
2) I replaced my Adcom with a B&K. The biggest change is that percussion like tom toms sound exquisite. I would love for someone to tell me what changed electronically.
3) I replaced my MonsterCable interconnects with homemade sliver. At first, I replaced just one cable. Wow! the soundstage opened up.
Before I made these changes my stereo never had a soundstage. The question is, if it is so much better, do I stop here? I think we all know the answer to that one. :-)
Back to your original question, to adjust or not to adjust.
What happens if your sense of hearing changes? It's possible that mine has. I feel very sensitive to upper midrange. Certain speakers just sound too grainy now.
My prime directive is to recreate the experience that the musicians had in my living room. So, I adjust my gadgets and gain knowledge that allows me to set up my stereo the "way my ears perceive it best." to quote Fbi.
Merry Christmas.