Your ignorance shines brightly. Controlling animals, and controlling suspects are two very different missions. I guess you have never busted through a door cocked and locked not knowing who or what was on the other side. The last thing on your mind is saving a dog; your looking for weapons in the hands of suspects. If a dog charges at you (or even looks like he might), you don't have time to get your pepper spray out and hope it works, you simply shoot the dog, and continue to cover any suspects that may be armed, and or continue to move through the house searching for any armed men. And if you did attempt to pepper spray a dog, you would compromise the safety of the guy next to you who is relying on you to cover your field of fire with your firearm (not a bottle of pepper spray).