It’s not about defense, it’s about a guy.
A guy brought up in a certain way that leaves him vulnerable to a “fatal flaw,” in this case drinking. Driving him to do so is the inanity he finds in the defense industry, along with sexual frustrations brought on by youth, exposure to society, his roommate Danny's porn collection, and beautiful Christene. One flaw exacerbates the other in a tug of war that will eventually destroy him (nearly).