There are any number of different preppers out there, some honest snd trustworthy, others like the “raider” idiot off doomsday preppers who interestingly was a felon in possession of firearms and went back to jail thanks to the show.

Build trust slowly, like any friendship, if you can.
Sometimes you are thrown together by circumstances and have no option but to work together and extend a certain amount of trust.

As to the “BS” Boy Scout motto, obviously NO was not a Scout and does not know how its applied in Scouting and life. As a current troop committee member and former Scoutmaster, I can say that it is the principle that has kept many alive, including myself.
It isn’t just a motto but a philosophy.