When I wrote my Zombie Objectivism post, what I had in mind with the "zombie metaphor" was the idea that despite Objectivism (the doctrine of mere selfishness rationalized to seem like a grand philosophy) being declared dead with the collapse of the economy it wrought and the admission before congress of its most powerful apostle, Alan Greenspan, that his entire worldview was wrong, we should not expect it to go away -- it will persist, "undead," but still roaming around, seeking brains. I argued the ways in which it is like (it is) a religion, in that its adherents are impervious to reason, and suggested we be vigilant against its inevitable return, which we can expect to be as destructive as ever.
But most of us know: reasoned thought does not begin with a theory and then set out to prove itself right. Reasoned thought begins with evidence and seeks a theory; if it has a theory, it sets out to prove that theory wrong. Once the theory has been proved wrong, it seeks a new theory with new evidence. To do otherwise is mere rationalization, not reason (even if it is logical -- things may be both logical and wrong), and it impresses none but the fool.
EDIT/ADDED: another apt use of the zombie metaphor, on another religious meme, from Pharyngula.