I dunno about what the backpacking community sayings,but I have a saying "Nylon Melts all over you in the event that your way to close to things that are on fire, inflicting horrible burns all over your body."
Now granted, there are some more fire retardant synthetics out there, but they would make for a pretty expensive set of BDU's
Having Spent a little time outdoors and carrying a pack, I would suggest to you that the backpackers saying ought to be "Cotton kills, provided you are silly enough to have brought only cotton and forgot all about basic thermal layering." Or maybe it should be "Gor-tex Saves." Because the one thing that no expirianced packer will ever be without, is a good parka (Winter, Summer, spring or fall if it looks like it will rain or not.)
I remember a novel written supposedly about an SAS unit, dropped in to look for SCUDs in the gulf war (I think the name of the book was Bravo 20 or something like that.) Anyway This bunch of SAS guys gets compromised and end up walking like half way across the Iraqi desert and it starts to snow and sleet on them. One of them eventualy dies from the elements. I remember thinking to myself Da*m, there guys are carrying like a hundred and twenty pounds of equipment and out of all of it, they did'nt bring a simple little thing like a Gor-tex parka. Call me silly, but I kind of think they would have been better off leaving a couple of pounds of that C-4 explosive at home and carrying a simple little thing lika a parka instead.
But thats just me...
All that being said your best bet, would most likely be Cabalas, they have a pretty wide assortment of Camo rain wear that may fit your needs.