While I'd never promote violence...I assume when you refer to SHTF...you're speaking of the end of a civilized society rather than just the inconvenience of hard times.
At some point in time you'd have to decide if you seek to survive. If the answer is yes...you'll have to do some pretty ruthless and demoralizing things to do so.
Never barter something that can be used to kill you.
I'm talking a couple weeks after an economic collapse. Tell me, what do I barter with, sunshine and rainbows?