I totally subscribe to that concept, and almost in those exact words. (I use the word 'demon').
While I can see what you are driving at, I cannot go so far as to suggest that all humanity is demonic, or at least in the sense that each_and_every_one is or must be possessed at some level. I DO believe that many, many are in fact possessed- Many more than our society is prepared to admit.
That we are influenced by demonic forces is unquestionable. Combine that to the thought that we are evil by nature (in the milder sense), and one can certainly see why the default "low" in human governance is anarchy. And so we go, ever slouching toward Gomorrah.
That our nation has almost certainly succumbed to the idea that Christianity is a personal thing seals our doom. Western Civilization, and Britain (and her whelps, to include the USA) particularly have succeeded because of a national sense of Christendom. We as nations subscribe to the Judeo-Christian Ethic as a societal sense of right and wrong.
Look not only to the laws written upon the books (which are enough to prove a sure connection to the Hebrew God), but look also to the laws written upon the heart: Note the close affinity between the early Brit concept of "the Stations of a Noble Heart" and the "Cowboy Code (Code of the West)" or the "American Way".
That societal norm is why kids here have been raised up to be good men and good citizens, and why for the longest time we could prevail against the evils that beset nations, families, and individuals, and even show progress in the war to bring about the Kingdom (it is all about the Kingdom, after all).
The infection of our society by the rotted root of Rome (by way of the Constitution of the French Republic's bastardization into the Socialist concept) is what makes these ills so prevalent in our nation- The supplanting of Rome's root for our Natural root is the direct cause.
The more that Natural root is cut away from us, the more we are grafted to the unnatural one, and why I can admit with good evidence, a fair subscription to the basis of this article.