In "The Things They Carried", why does O'Brien relate his experience as a pig declotter?

In the section of his book The Things They Carried titled “On the Rainy River,” Tim O’Brien describes the period of his life when he was inducted into the army to fight in war the purpose of which he found uncertain and the shedding of blood within which he found nonsensical.  After this discussion of his political opposition to the war and the somewhat ambivalent approach he had taken to express that opposition, O’Brien pauses to relate the story of when he worked at a meatpacking plant in his hometown in Minnesota.  His job was removing blood clots from the necks of the dead pigs, a position for which he labeled himself “Declotter.”  O’Brien provides a detailed description of the process by which the pigs are slaughtered and gutted as part of the process by which their remains are processed into food for human consumption.  In relating this story of a position he held prior to his induction into the armed forces, O’Brien is drawing a parallel between the slaughterhouse and the slaughter to which he would soon become an integral part: the war in Vietnam.  Describing the sensations that accompanied his work in the meatpacking plant, the author writes the following:

 “At night I'd go home smelling of pig. It wouldn't go away. Even after a hot bath, scrubbing hard, the stink was always there—like old bacon, or sausage, a dense greasy pig-stink that soaked deep into my skin and hair. Among other things, I remember, it was tough getting dates that summer. I felt isolated; I spent a lot of time alone. And there was also that draft notice tucked away in my wallet.”

O’Brien is indicating that he is transitioning from one slaughterhouse to another, and that, just as he could never quite cleanse himself of the stench of the meat plant, he will be unable to ever fully rinse from his body and mind the stench of the bloodletting he will witness in Vietnam.