I don't know about many of you, but I mostly play Call of Duty for the zombies now-a-days because I am completely enthralled in the story along with the mysteries hidden within the levels. The Zombies mode is far deeper than the simple goal of survival it provides. Now not many people know this, but the songs themselves tell stories and explain the motives behind many of the characters in the Zombies story line. The only exceptions to this are the licensed music by Eminem, Skrillex and all of the music provided by Avenged Sevenfold save for Not Ready to Die which was a completely original song produced by them in conjunction with Treyarch.
If you haven't heard the easter egg song in Tranzit, I suggest you do so. It is pretty decent and if you listen to it carefully, you will notice something. This song basically confirms what "The One" tried to get across when you activated it on Shi No Numa. The zombies are not unfeeling, they know EXACTLY what they are doing and they can't help it. They have no choice but to give chase when they have set their sights on you. They are a slave to the other worldly presence commanding them to attack you, in this case it is Edward Richtofen, the crazy Nazi scientist that switched bodies with Samantha on Moon. While they don't want to kill you, and they most certainly regret doing it when they do, the primal impulses driving them to attack and eat you gives them a type of physical pleasure when they do so.