As if your word on anything has any value. A .223 is a puny round by sniper standards. It's easily deflected and just isn't very powerful compared to more common rounds like a 7.62 mm. Sure, it does a lot of damage when up close and personal, but if you check back to the guy's first shot, you'll see just how ineffective a round it is. The guy attempted to shoot someone through an ordinary plate glass window at a store. The bullet just made a hole in the glass but didn't hurt anyone inside. A 7.62 mm round wouldn't have that problem.

As for marksmanship, check out the ordinary firearms training every Army recruit has received in Basic Training for decades. A 300 meter shot with ordinary signs is standard. The human shaped target only stays up for a few seconds, so when the shooter is in move-out mode, he quickly has to decide to take the shot while standing (low probability of a hit) or to take the time to get into a kneeling or prone position where accuracy improves but you have to rush the shot. It's all standard.

As for the rubes, you wouldn't even make it up to their level. I've never seen someone this side of Lindy who is so willfully ignorant on so many topics as you.