Ripsnort, that was a paddle holster, a standard belt loop kydex holster can't be stripped by that technique when properly defended. Also, the guy wearing the pistol was using improper, as in NO retention techniques. When you need to defend against someone trying to snatch your weapon from an outside the waistband holster on your belt, you grab underneath the bottom of the holster with your fingers, and pull it out, like a submarine's dive planes extending out, so that the top of the weapon is dug into your body, and the muzzle pointed in as close to a horizontal plane to your side/3 oclock as possible. Pivoting/spinning the weapon side of your body away from the threat is easy at that point, as there is no way for a threat to pull the pistol out, as it'd have to go through your body to get out of the holster when it's pulled out and up in this manner. This is the best retention technique and it works with any type of belt holster, and will work with paddles as well, just not as well, as they are much less secure.
There are other retention methods, but this one is the fastest, simplest, and in most cases best IMO, and works with most open carry belt holsters of any retention level, drop holsters as well. CCW/IWB holsters is a different deal.