So, I say a 7mm Mag isn't a sufficient deer caliber because it has way too much knock down power.... more than enough needed for a thin skinned, thin ribbed whitetail.
You do understand that "insufficient" and "excessive" are opposites of one another (they are antonyms). Insufficient means "not enough," so if something works but is "way to much" then it is most certainly still sufficient. We're talking about whether it's sufficient to kill a deer, and even in your anecdote, it obviously got the job done in spades. The 7mm Magnum, as I believe I stated, is more than sufficient for taking deer. As I also stated, it is also quite capable of causing a level of damage to the animal that one may find excessive, hence it being overkill.
I think that you are confused between what is sufficient, ethically and practically, to kill a deer, and what is optimum.
Mike