Yeah. I guess I would consult a lawyer first, about the best way to do this.
Seriously though, this dealer's response is totally ridiculous. How do they know it is "perfectly driveable?" Did they look at battery capacity, or the 96 cell voltages? I have a $30 OBDII adapter, and a $5 app that can tell me these vital things in five minutes. They couldn't be bothered to do as much?
"There IS a reduced range with cold temps." Are they that stupid, or just being smart a$$ed? A total range of 142 miles on a 100% charge is grounds for a warranty replacement, but 86 miles or 36% is "perfectly drivable!" GM has a huge problem with their dealer network...and the rest of the old-line OEMs are no better.