That may be the point he's trying to make, but there is not a single person who is in favor of gun control legislation who is going to take that message from this demonstration. And that's an important consideration. Is he trying to convince people who already hold his point of view? Well, no, obviously there's no need for that, they already agree with him. Is he trying to convert the Piers Morgans of the world? Well, he chose probably the worst possible method to make his case for that group of people. So what's he going for here? If anything, this sort of display strengthens the minds of anti-gun people even further, because I don't care how pro-gun you are, you don't want to see people carrying AR-15s around when you're doing some random shopping.
And, FYI, this is coming from someone who is staunchly pro-gun. I believe it's everyone's right to own a firearm, including some of the stuff that is currently banned. I also think people should exercise some common sense. Just because you're legally allowed to do something doesn't make it a good idea. As others have said, you can burn a flag, but that's not going to endear people to your cause. I don't care if you carry a pistol with you, but if I see someone strapped with an AR-15, or any long-barrel gun, or multiple guns, in a public place, I'm making myself scarce. I don't know that person's motivation, but I know that that's completely over the top for personal self defense, so they might be out to shoot a whole bunch of strangers, and I don't want any part of that.