really? where? what are they hunting? a .223 caliber bullet doesn't kill much wildlife.
ARs can be chambered in anything from .22 to .50 beowulf. .223 is a pretty good round for ground hog, prairie dog and coyote and remember we are allowed to use expanding/fragmenting rounds here in the US of A.
The AR my pops just bought chambered in 6.8 SPC was used to hunt antelope in AZ and will make a damn fine Deer slayer as well. Nothing wrong with using the AR as a sporting weapon. Hell most of the popular hunting rifles through our nations history have started out as weapons of war.