I'm also in the "run it wet" school, but by that I also mean "heavily lube the shiny spots" rather than slathering the whole bolt and bolt carrier assembly in oil.
The only spot that is susceptible to carbon build up is the stem on the bolt behind the gas rings. And that's not really a big deal. You can get a tool to remove it, you can just use some solvent and an old bronze bore brush to keep it knocked down to minimal levels.
Consequently, I'm not in the "lube it with synthetic motor oil" school of thought. Break Free / CLP works fine (and the civilian stuff smells better than the military stuff), and LSA worked fine way back in the day for that matter.
FWIW, I agree the guy at Gander Mountain is ignorant. It's hard to blame him though, as it's a common misperception - one that took awhile to dispel in the sand box, where the belief was that running them dry prevented dust from sticking to the bolt and carrier. Dust will do that anyway, and with no lube to reduce the friction it just increases wear and causes stoppages.