The show cars don't get terribly dirty, you're right, but my drivers do, and my standards are the same for either, I wouldn't foul up the finish on my truck any more than I would that freshly restored T-bird.

Water and suds, water and suds... The type of dirt that covers a car from rain-spray and general road grime does not require ANY heavy pressure to remove, so any scratches that result from washing a dirty car would be from totally-unnecessary "rubbing". I do notice that alot, people washing their car with all this pressure and scrubbing going on, going over one area multiple times, like they're trying to scrub a pet-poo stain out of a carpet, as if that's what it takes to get the car clean, not realizing that all the dirt lifted away into the soap on the very first pass. They're the cause of their own damage, not the mit, or the brush, or the towel.

Regarding your dealer, you're trying to draw a conclusion upon an isolated incident rife with potential causes/variables.

He could have had a piece of grit in the towel, or the towel could have had sand/dirt in it from the ground, or from wind blowing it into it, or the towel could have been some stiff and crusty to the touch (not soft) Sam's Club shop towel, and on and on... All towels are not created equal, and I've become quite a connoisseur in my lifetime!! I keep "the good stuff" in one cabinet, and the "crap" in another for dirty unimportant jobs. I've found that the towels sold by detail boutiques like Griots really suck... They're soft, but they don't absorb, and they pull-threads like a home-knit sweater. I'll never waste that money again.

And contaminants that scratch paint can blow into or be picked up by ANYTHING you use, wash mit, towel, micro-fiber, chamois, you name it... Your best hedge against grit is for there to be a degree of "nap" in the rag/mit/yak-ass you're using.. Since dirt and grit is fairly small, you don't need 3-5 inches of brush nap to allow it to escape from the working area of the medium, the nap of a good quality soft towel is more than adequate to carry off a few panels of dirty car, then rinse and continue, as you would normally wash a car.

Quite honestly, it's the micro-fiber towels that have very minimal nap, and therefore have less escape-area for dirt that's introduced. The WORST is the chamois... You get a single piece of tiny grit unknowingly into a chamois, and you can trash your paint job. There's nowhere for the grit to lift into, it stays right between the leather and the car, scratching full-force.

Micro-fiber towels and chamois are fantastic when used in a perfectly dirt/grit free environment, like classic cars for instance, where dust is usually the primary filth.

But I stay away from those when washing and drying a really dirty road car, as you're going to have areas (like wheel openings and exhaust cutouts and lower rocker panels) where un-washed-away dirt may get accidently or unknowingly wiped over while drying, contaminating whatever you're using. In those cases, the deeper the nap, the more room the dirt has to get away from the surface, and the less overall pressure pushing the grit against the paint..