I know some people think that the SFB universe is just plain wrong, but I would like to point out that until the movies and STTNG came along, it was all we had. The first few movies didn't show anything that showed Starfleet in a less militaristic light. TOS had plenty of instances where Kirk wasn't exactly handing out olive branches. It was always assumed that a Klingon or a Romulan was an enemy. The Federation had had wars with them and was in a cold war during the series. There was a little incident with the Gorn (they only destroyed an outpost), the Tholians (trapped starships in their web). To me, the TOS Starfleet was a military organization. Exploration was one of its duties and maybe it chief peacetime concern, but it's other job was defense and to train for that you have to train for war. Sorry.
babbling and venting.
Heck, even Riker considered himself a soldier.
"Retreat?! Hell, we just got here!", annonymous American Marine, WWI
"Gravity is a harsh mistress....", The Tick