Now to comment on the skeptical side of things again.
Benny Hinn got ridiculously rich showing both the educated and uneducated, the simple and the smart, the mentally disturbed and the mentally healthy supernatural feats. And he was a crook and a fraud. Simply saying that you are a sane person not prone to flights of fancy is meaningless. James Randy is an ex-magician that works to disprove supernatural phenomenon, he says his background as a magician helps because even scientists can be taken in by illusion if they aren't careful. The reason for this is because belief in our personal experience is hard to fight, even though it is one of the worst gauges of reality. It took thousands of years to come up with the scientific method, a means of removing person experience from the equation by relying only on that which is verifiable, quantifiable and predictable amongst a peer group using a solid methodogy meant to remove the uncertainty of personal experience. Prior to that reasoning on the world was done by experiencing it and then rationalizing those experiences. That's when we lived in a demon haunted world. Once we actually started reasoning rather than rationalizing, the demons, and gnomes, and mystical forces magically began to disappear. And the one's that remained were consistent only with the cultures and ideas of the people that experienced them.
Your hypothesis that skeptics never see demons because Satan is hiding from them is also disproven just by the fact that at least one atheist in this topic has experienced "spirits" or whatever, and there are others in the topic that have experienced "wierd things" but do not attribute them to demons. Your hypothesis would only be true if the nature of the demonic visit was expressedly unambiguous. The demon would have to say "Good evening sir, I am a supernatural entity you call a demon (A biblical one, not a hindu, or wiccan, or other kind of demon, those are make believe), now if this is a good time for you, I will proceed to haunt you. Don't take it personally, I'm only doing this because you do not have the divine protection of the Father (that's the christian god.), let's proceed with the haunting." If I had a book that wouldn't burn, my first thought would not be "holy crap, it's a demon, let me get my bible.". My first thought would be "this is highly interesting, let me remove it from the fire and begin documenting this and testing to find an explanation as to why this is so." Strangely enough no person having demon experiences ever seems to have the presence of mind to take this tack, and instead they do something that immediately ends the demon encounter, once again restoring natural order.
Furthermore that brand of reasoning renders any statement equally true. The only reason YOU don't know that our government is run by aliens is because they don't want you to. But that guy in the tin foil hat, he knows the truth. The only reason you haven't seen any hobbits is because they are so good at hiding from humans, but that chubby guy at comic con wearing the Gandolf costume, he's seen them, tolkien saw them too that's why he wrote about them. See how easy it becomes to justify anything if the reasoning behind it is that there is a concious agency that doesn't want you to know about it? When things patently false can be justified using a line of reasoning, then the line of reasoning probably should not be relied on because it lends no credence to that which you are using it for.
With phenomenon that are consistent with what you'd expect from psychologically and culturally motivated experiences such as demon attacks or talking with god, or monsters or visitors from the stars it always comes down to the individual insisting that everyone else may have mental problems, or are easily fooled, or are deluded in some way, but not me, I am not like that, my experiences were for real...and they all say that....which is what you would expect from psychologically motivated experiences.