Re: "I'm a soldier not a diplomat."
TOS was inconsistent on many levels, more than most of the new shows in fact. I prefer to think of Kirk the one-dimensional military man to be a product of the same effort to establish the show as UESPA and the like. If Kirk was always written like this he'd be a distasteful character. Compare to Picard...prepared to fight a war in Redemption, but very reluctant to do so.
It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring. Carl Sagan