A couple things to remember related to this:
1. How many of these people actually understand farms are where food comes from, and know where they are?
2. How many of these people have the initiative and determination to go to such places if they know about them/
3. How many of them are actually within even multiple days journey of such places?
4. How many of them can navigate without GPS?
There's several similar considerations, but the long and short of it is that in a Carrington event situation, there's good reason to expect that there'd be small groups of stragglers, not large mobs, heading out of cities and looking for food. Some of those people would absolutely be people with a past penchant for violence, but it's going to be very limited quantities, and most likely only after they've used violence to take food from other people in cities.
I'd expect a lot more heavy raiding of suburbs before attacking outright rural dwellers becomes an issue.
Honestly, there'd be so many moving parts and so many fine details in situations like this, and so many different major urban areas, that you'd probably have all kinds of different scenarios playing out.