I can understand where this guy might come from but truth be told, it's not "a gun" that is the only problem. It may not be a semi-automatic rifle, but one can load any rifle with a solid copper tip bullet and only a small canal wound be on the body, some of the tissue will be dead as well, then one can load that same rifle with an open lead tip bullet and you'll have a small entry hole, the size of the bullet and an exit hole the size of anything between an orange and a small melon, depending on where the shot was landed. Using different types of bullets for any weapon will wield different results.
The AR-15 is dangerous, as any gun but is also just an extension of the hand that holds it. A semi-automatic weapon can mean the difference between life and death in self-defence, an automatic weapon however has no place in civilian society.
I'll probably be executed for this but...From the news and reactions (I have no firsthand experience of any of this, so it is only my opinion on how your news is portrayed here and what is shown and what not) of some of the US population, they are so fixed on defending their rights that they lose sight of the implications and to a degree the meaning of the right. Now I do realise that more hillbillies than civilized folks are interviewed, but some folk's mentality who have been on the news would never be allowed to get within 30 feet of a gun in these parts.