Another reason for the censorship of truth is that it can be dangerous to a society as a whole, not just the elite and those in power though that should not be discounted, but because truth or new ideas can threaten the entire foundation on which a society stands, primarily it's belief systems: political, economic, social, scientific and religious. Therefore, truth is never a popular or comforting thing to many people.

Even creativity is controlled and censored in societies to different degrees, since too much creativity can lead to new ideas, and discovery of new truths, which may threaten the legitimacy of any system no matter how open to the truth it may claim to espouse. For example in ancient Greece during the time of Pythagoras a mathematical religious style cult had formed around Pythagoras and his followers having a substantial amount of power and influence. The Pythagoreans' even knew mathematical equations which could disprove their idea of reality, but these formulas were not to be spoken of or revealed, doing so would most likely result in death. The concept of the number 0 was considered too dangerous at the time and ignored, as well as for another 1500yrs, though one mathematician at the time Zeno, used a mathematical paradox with a partial concept of 0 in it, which could not be proven wrong, giving the Pythagorean reality a thorn in its side. Zeno's use of a riddle is what most likely kept him safe for criticizing such a group, similar to what Ben explained above about the use of satire and comedy as a form of criticism. Some good historical examples of this would be In Praise of Folly by Erasmus which helped start the Reformation or Voltaire's writings such as Candide, which helped to contribute to the Enlightenment. This list could go on forever, and many people who have threatened the status-quo of any society have usually found themselves imprisoned, exiled or killed. Academia and other artists or writers are no exception to this rule; very few people defended Machiavelli, De Sade, or Shelley. They all paid a price for telling the truth: Shelley was thrown out of Oxford University for his essay The Necessity of Atheism which attacked the moral authority of his time, Machiavelli was tortured and exiled for simply explaining how a political power structure works in The Prince, and De Sade imprisoned for using pornographic symbolism in his works to show the true vulgarity of any power or social structure in society, which still applies to this day. Also, the attacks against women's rights throughout history are yet another example of censoring truth, and in this case half of the human race by gender (one's biology). The prevailing reality for centuries enslaved women as second class citizens and property; they were thought to be incapable of doing much more than making beds and babies. Even in the so called enlightened West women still have yet to be free from the untruths imposed upon them by modern reality; only a few years have passed since women were given full suffrage in Switzerland in 1990.

So, in the end truth and reality are at odds; reality is usually simulated by a society or culture to maintain it's control, and methods employed such as, censorship or more extreme measures will be taken, in order to prop up the prevailing reality. The repression is carried out usually with the help of those who follow the herd or "sheep and goats" as Don Henry Ford states in the above comment. My conclusion would be that any truth one may wish to unleash in order to enlighten the world will be meet with resistance, and the more threatening the truth the greater the response to repress it, and at times even form unlikely allies between so called traditionalists and radicals at any given period in history.