Is it a bit far fetched? Sure, but the point I'm trying to make is that 2013 Manhattan filled with people who probably would struggle to start a fire because they've spent their time playing with their iPhones, makes for a very different target than hardened rebels who can survive in harsh conditions. Look how white collar, urban professionals struggle when they go on Survivor TV show, and then the producers give them some food and water.
Bring them down to the level of having to fend for themselves in a very old fashioned way, and you've got them on their knees asap.
If we were like Afghanistan, or like anytown USA circa 1800, then yes, being able to shoot back would be the most useful ability to have.
Someone going thru Facebook withdrawal who hasn't even gone camping in years would soon be more concerned about getting food and water than almost anything else. Modern urbanites are wussies now, compared to their ancestors.
Although I do have to admit, having more firepower than your neighbor might help you take his flat of bottled water, but that's not quite what the 2nd amendment is for, is it ?