I doubt that your instructor was actually condoning you going out and hunting deer with a .22 mag.

I am sure he was simply trying to convey how even some of the smallest cartridges can be capeable of killing even large animals when in the hands of very skilled hunters.

The .22mag is more than capeable of killing any deer that walks this planet. Even elk and moose. Put a bullet of any size where it needs to go and the result is a dead animal.

Did he add anything to this statement before or after? Any other context that goes along with it?