This is why people who aren't knowledgeable about guns, or come from countries not in a gun culture, should stay out of gun debates. They generally don't have a clue what they are talking about. You can fire just as many bullets, and just as fast, from a pistol that carries 6 bullets as a so called assault weapon. (even using that name shows lack of knowledge on the subject).
Magazine size, reloading times, pistols, rifles, AR-15's... a dedicated person can kill the same number of people with any of them.
This video is primarily showing why magazine size limitations are incredibly stupid. But notice at one point they demonstrate how to fire 30 rounds from a 6 shot revolver in 18.8 seconds. And if you pay attention you'll notice the 6 shot revolvers fired faster than a semi automatic with higher magazine capacity. They also show a 100+ year old designed pistol shooting 21 rounds in under 10 seconds. And that was with 3 reloads. Assault weapons weren't close to being invented yet.
I put "assault weapon" in quotation marks because I was quoting Bocefish (who posted that very same video). With the AR-15, you can legally purchase a 100 round magazine. I'm going on the assumption here that you can't just walk in to a shop and purchase 20+ 6-bullet cartridges (I would hope that's true or things are even crazier than I imagined). I just don't see an argument for the AR-15 and other guns like it being remotely necessary or less dangerous than the average pistol. The other argument here is that the average person will be able to do more damage with something like the AR-15 than with a pistol they will have to reload every 6 shots.