The .223 round used in the AR-15 isn't really powerful enough to hunt deer. You are more likely to simply wound one, then lose it in the brush. And to a true sportsman, that's a real waste.
.223 is only used for very small game and varmints.
You may ask: but what about humans? The .223 is designed to wound a human, not kill him. A wounded soldier is no more effective than a dead soldier, but consumes a lot of resources to rescue and treat him.
That's the politically incorrect version, but it's the truth.
The 223 is a legal deer round in Ga and many other states. It is as effective on smaller south eastern white tails as a 30-30.