Flip Romney's disdain for the military seems to go back to 1968, when he was hiding out in a mansion in France being waited on by servants. His father George, Governor of Michigan, was actually THE leading candidate for the Republican POTUS ticket at that time, leading Nixon by more than 12 points. George met with some military brass to talk about the Vietnam War then afterward he was quoted in an interview that the Generals were trying to brainwash him. Of course this did not go over too well with the Right-wingers and immediately George's number began to fall.
Eventhough Mitt was sipping cappacinos in southern France, he was very engaged with his father's run for POTUS and this bad turn had a profound affect on him. And it seems like Mitt has had a bad taste in his mouth toward the military ever since.