A person is innocent until proven guilty.
In the past, I've found myself guilty of taking that sentiment and generalizing it to mean that all ideas or notions deserve the benefit of the doubt.
In other words:
Any given idea should be considered creditable until proven ridiculous.
But that's not quite how "innocent until proven guilty" generalizes.
"Innocent until proven guilty" really means:
The prosecution bears the burden of proof.
A prosecutor cannot simply claim that someone has committed a crime. The prosecutor must support the allegations with evidence and then argue his or her case in the Court of Law.
All claims have the same burden: an idea or a notion does not inherently receive the benefit of the doubt. On the contrary, a claimant must carry the burden of proving any claim in the same way that a prosecutor must prove the guilt of a defendant.
That is why a person is innocent until proven guilty. A person should not be punished until a thorough, justifiable argument has been made which is supported by verifiable evidence.
This is nothing more than another flavor of skepticism.
This form of skepticism is designed to deter anyone with great authority from whisking you away to some cold dungeon or tying you to a stake and burning you alive.
This mechanism prevents someone from making frivolous claims against your person-- claims which could easily condemn you to a tortuous end-of-life. All because you were simply accused.
Skepticism allows the questioning and challenging of ideas. Skepticism is simply freedom of thought. But this simple-- yet powerful-- ideal works towards protecting us from being constantly bullied by people of higher authority.
And where there is freedom of thought, freedom of expression tends to follow. These two principles serve as the vertebrae of any free society. The United States was born out of a movement of enlightenment and skepticism.
Here then, is another reason why we so desperately need skepticism. A tyrant desires an society that subscribes to unthinking belief.
But where there is skepticism, liberty is not too far behind.