Not necessarily. The guns and ammunition are more valuable. You could trade them (or your time in protecting them) for the other things without stealing.

Besides, I think it's a moot point because I know a lot of preppers and they're all very aware of concerns like safe drinking water and food.

>seem to be preparing to become the people who would take others' food and supplies by force in the event of a real nuclear war level catastrophe

Or simply preparing to defend against those sorts of people.

The thing is, "those sorts of people" don't really exist. There have been PLENTY of disasters resulting in short or long term societal collapse all over the world in the last century, and none of them resulted in widespread banditry.

Didn't ISIS do that in Iraq and Syria? Kidnapping is also a common way for armed people to get money from others in insecure countries, possibly more than they could get by directly stealing their possessions.

ISIS didn't arise spontaneously after an earthquake. It was intentionally built over a period of 10 years by a coalition of political parties and religious movements as a continuation of the insurgent war against occupiers, with the eventual goal of establishing a new society with new laws: their mission was inherently social and cooperative (by means of military conquest).

That's hardly the prepper expectation of "there will be a solar flare and then the whole world will instantly be filled by roving gangs of psychopaths, like in The Walking Dead"

They are simply preparing for those "people who would take others' food and supplies by force" in any type of event.