Arthur Silber quibbles over the definitions of "closed" and "open" philosophical systems, but I don't think he gets it quite correct. According to Silber, a "closed" system is one that, according to Paul Curtis, "subsumes all discourse into its own unanswerable internal logic." An "open" system is, "identifies certain broad principles... and that many additional implications and much additional knowledge can be built upon those principles." I think Silber is correct when he notes that all philosophical systems are in some sense "closed" and in some sense "open".
Silber has probably correctly identified how many people think about "open" and "closed", but when binary, opposite terms fail to draw an actual distinction in some context, we should look around for a distinction to apply them to, one that preserves the intuitive, prosaic meaning of the terms. One straightforward distinction that seems a good candidate is the degree to which a philosophical system will change based on perceptual or experiential evidence.
No system can change completely: It is difficult to see how any logically possible evidence could change the fundamental principle of metaphysical naturalism that the evidence is all important. But everything else under metaphysical naturalism can change according to the evidence. Contrast metaphysical naturalism with any brand of theism: It's not that there's something that doesn't change according to the evidence, it's that theism changes nothing at all according to the evidence: The whole system defines perceptual and experiential evidence as irrelevant and outside its "magisterium".
The fundamental premise of metaphysical naturalism doesn't embed any actual knowledge in its premises: We cannot use pure logical deduction to obtain any true statements about the world. It is thus epistemically "open": knowledge is not embedded in its metaphysical premises. A purely deductivist philosophy, e.g. theism or Soviet Marxism, on the other hand, either embeds actual knowledge directly in its metaphysical premises, or circumscribe what is considered "evidence" to either a finite, closed set of statements (scripture) or a metaphysically privileged priesthood or party.
All philosophical systems—indeed all language—exists to make distinctions: between sense and nonsense, true and false, knowledge and fantasy. To say that all philosophical system are the same because they all make distinctions is to ignore how these systems make distinctions. Just because all doors have a doorway does not mean that some doors can be locked and bolted and others can be wide open to the evidence of our senses and experiences.
We can then talk more precisely about what constitutes a specifically totalitarian philosophical system: A epistemically closed (in the sense above) philosophical system which is also ethically closed to moral intuition. It does not matter how you or I or anyone—or even everyone—actually feels about the horrors which have been perpetrated in the Iraq war: The rightness, the justness is embedded in the metaphysical ethical principles. America is good, and Iraq bad no matter what the evidence of our senses or our moral intuitions. Any evidence is either shoehorned into compliance with these metaphysical principles or ignored completely.