There is deer and then there is deer, there is hunting sitting in a cozy stand on even ground to in the wide open sage brush or heavy timber and steep rugged mountains, warm sunny days to freeze a$$ blowing snow hunting.
Plenty of things can and do affects the size of the animal and or how the shot is or should be taken. I have shot deer where a 223 woulda been just fine and then like earlier this week I woulda hated to have shot the two we did with a 60 grain bullet for far more reasons than I am gonna get into here. Situations are different in different areas and a guy otta use what he knows is right for the hunt he is doing, not just cause if everything is right and it can.
Ya gonna shoot a small animal from a stand where you have all the time you need to make that perfect shot on a grazing critter or are you hunting in rugged terrain where the animals tend to be fairly good size, and if your lucky will stop a very few seconds and give you a quick off hand shot?
It isn't fun if they run to the bottom of a 60 degree hill and your gonna have to drag em back up outa there.
I don't even wanna hear this "deer NEVER run if you hit em right" Killed and seen killed far to many to buy that. I have shot deer through both lungs that ran a couple of hundred yards blowing chunks of lung out as they went, others collapse never taking a step.
Blanket statements that a guy can't shoot straight because of the fact he don't use what someone else thinks is enough caliber don't seem brilliant to me. In a nut shell I would say don't send a boy to do a man's job, person or caliber it just ain't real smart.