Before the AR's, a .22 centerfire bullet was never considered adequate for deer. Not by hunters, not by writers. There were soft tipped bullets back then, too. So what changed, just the popularity of the platform it's shot from suddenly makes it OK?
Shooting a large game animal like a deer with a round that's acknowledged to be barely adequate, and only under certain circumstances, is not OK to me. I'm sure some poacher in Africa has killed an elephant with an AR, that doesn't make it an elephant gun.