I've been trying to come up with a scenario where a citizen would need to defend himself from a governmental agency in the US. It isn't happening. And I think that played into the 2nd amendment back in the day. We were breaking away from a restrictive government and there just wasn't a proper infrastructure for the new government to defend each individual citizen. That's without mentioning the natives who were somewhat of a threat. And, of course, hunting for food. It's almost like you really did need a gun if you didn't live in the most populated areas.
Trying to apply that logic to present day, we no longer need guns to defend ourselves from foreign governments. I doubt Canada or Mexico are planning a ground invasion. And despite what Patrick Swayze went thru, an invasion from the sky is even more unlikely.
We still need guns to hunt. No idea what percentage of the population actually hunts for it's food but I'm sure it's pretty small. I imagine a similar percentage of the population needs protection against wild animals. Either way, there's no denying that there is a requirement for some firearms for a small percentage of the US. But they're not living in cities.
Finally, I suppose you could replace "natives" with "criminal element". This is where you could make a case for ALL individuals owning a gun. You can be the most "surroundings" conscientious person on earth but still end up in a bad situation as criminals are free to travel the same path as you.
While I don't think banning AW will prevent another mass shooting, I'm having a tough time figuring out why anyone would actually need a gun capable of firing 100 rounds a minute. Again, if a grizzly bear was charging me, I'd want a bazooka. However, I'm pretty sure it's ilegal to own a bazooka. Banning guns with more than a 10 round clip seems like a no-brainer. Beyond that, it just seems like you're trying to placate an outraged, hysterical group.