MMario,
With all due respect...
that's not been my experience.
Lots of things that clearly don't involve matters of personal taste are very debatable are not at all cut and dried. To me, at least.
On the other hand, for people who hold unshakable beliefs about those matters they might indeed be cut and dried.
Check any news broadcast for lots of examples.

Liz,
If the thread title made you curious, it served its purpose:)

Buck,
The key word is "argue." I assume the elderly Asian gent wanted an explanation of a preference rather than to begin a ebate/argument/dispute about the preference.
I don't think that "de gustibus" is about elucidating preferences. I agree that there is much to be gained from such.
"De gustibus" is about getting other people to adopt one's personal preferences.
Sometimes the assumption seems to be that if someone "understands" my personal preference it will become theirs.
Sometimes the assumption seems to be that I can verbally bully someone into adopting my personal preferences.

I've seen both on Mudcat.