First of all that firearm is not an AR15 rifle it is a Sterling 9mm submachine gun or SMG. I used to carry one when I was in the Forces, it was the firearm issued to armoured soldiers as it was easy to fold up and maneuver with it in a tank, lynx or APC. The range on that this is maybe 50 ft. max and in no way equals what the shooter was using. First media false news item. 

Of course the NRA is going to protect gun owners and I would expect nothing less. Has the car industry banned cars yet for the terrorists driving into crowds? No. How about 9-11 and box cutters. Again no. 

Everyone calm down and take a pill if you have to. Maybe go on the NRA website and see their good works!