Those types don't expect Preppers to help - they expect to FORCE the Preppers to "help".
I would guess most preppers are not visualizing dealing with decent, honest Americans when they purchase firearms and ammo. In my case, I'm imagining my neighborhood Obama voters, people who think they are entitled to take what they want from others. No one is morally entitled to take. They may have the power to take (and government makes that much easier), but stealing is always immoral. In the absence of government, I want to make sure I have enough power to protect my property and my family from thugs (i.e., liberals).