Being able to differentiate between reaction and response in arguments is generally the difference between winning and losing.
Actions have consequences. Military actions have very big, wide-ranging, and long-lasting consequences. However, military actions are ultimately within our control. Who we vote for, what we vote for, what we support and what we condemn, are all elements that directly shape our ideas of the military and its use. Understanding these issues is a necessary part of functional democratic participation, as well as an ethical engagement with the world.
A structured system of how knowledge works helps us use it better, and recognize where we may have problems and weaknesses. Understanding the limits of knowledge explains why knowledge alone is not enough to make us act a certain way. (How many med-school students smoke?)