I don't see the point of arguing his credentials or even if the story is true or not.
I'm a supporter of the 2A and think I should be able to own even fully automatic weapons. I think he is wrong headed about the need or even the legitimacy of even owning an AR rifle. I don't think it's something he will even consider.
I however, do have concerns about gun culture. Unfortunately, among us there are people who are complete jerks to others who are not like them..... race, religion, sex, politics, wealth, status, etc. Many are vocal about it. There's also plenty that have poor muzzle discipline or do other inconsiderate things with a firearm and not a care in the world. Many who don't care who they sell a gun to or buy one from.
Those people are the cracks in our foundation.