Why we need normal capacity magazines

Is this video a good enough reason?  If a group of men violently attacks me, should I really be restricted to 11 rounds of ammo in a gun that fits 16? 

I live a quarter of a mile from a housing project in Boston.  There are gangs around, they have guns, and they do stuff like this.  What happened in this video is what I fear when I'm out walking my dog at 11PM.  This is why I carry.