I just came upon that video last night. A few problems that he didn't address is your skin and a determined attacker. Your skin is very tough and elastic. The 'give' absorbs alot of the punch as the birdshot spreads. Put on a coat or heavy shirt and it becomes more so. Have you ever heard...
I have a tree care service. On Saturdays when I can take off, I usually visit a certain gun shop. The old man in the back 'Leroy', always calls out "Hey treedoc!"