I'm pretty much with Tiltsa here. It seems very obvious that there is much more to this story than the disgruntled guitar owner is telling.
I don't have strong feelings about Carvin one way or other aside from having a touch of hometown fondness because they are a company that was founded in my little city and grew enough to outgrow it. I spent many days in the original factory/showroom as a young musician ogling the massive 32x8 mixing desks and other stuff that was way out of reach.
Anyway, I've owned Carvin stuff. The live sound gear was great stuff. My Carvin guitar was one of the best playing and most well built I've ever owned. I've also seen plenty of Carvin items that did nothing at all for me.
Their customer service has ALWAYS been awful. Anybody who says otherwise, is either lying, lucky, or just one of those people who asked no questions and simply exchanged money for product.
They have a reputation for outright customer contempt, and they earned it. That's a fact. When I was 19 and had a few bucks in my pocket, I decided to buy a complete live sound package for my band. I walked into their Factory with a stack of C-Notes and a list:
MX2448 24x4x4 mixing desk
Mosfet 900 power amp
Mosfet 400 power amp (x2)
15" passive mains loaded with EV speakers (x2)
12" passive floor monitors loaded with EV speakers (x4)
19" touring rack/flight case
Mixing desk flight case.
It came out to just shy of $10K (in 1988 that was a metric fuck ton of money).
I bought this stuff directly from the building the items were built in. No middle man, no shipping, nada. When I asked what the "best price" was after totalling it all up, the guy says "list price. We don't negotiate."
"Ok, fine. I'll take it. Can you throw in a snake?"
"No, but I'll sell you one for list price"
"How about just a couple of XLR cables?"
"No."
"Uh, ok. Well, here's your money. Can I get some help loading this stuff in the truck?"
"No, but you can park by the loading dock so you don't have to carry it as far."
"Thanks."
"Sure."
Yeah, so that was pleasant. Sadly, from what I have heard over the years, my experience actually WAS pretty pleasant by comparison.
So having said all of that, it sounds like this dude had already somehow managed to get these assholes to capitulate on some level by letting him return a guitar in the first place. He should have bought a lotto ticket that day.
The fact that he's now throwing them under the bus over such a ridiculous situation tells me that he's a more egregious dickhead than anyone at Carvin, and that takes some serious commitment to pull off.
All things considered, and based on what I know to be true, I'd say the response from Keisel has been shockingly measured and polite.