"There is no sin except stupidity." - Oscar Wilde

"Intelligence is the capacity to receive, decode and transmit information
 efficiently.  Stupidity is blockage of this process at any point."
 - Robert Anton Wilson

"The trouble with the world is that the stupid are cocksure and the
 intelligent are full of doubt." - Bertrand Russell

Five fundamental laws of stupidity:
 * Always and inevitably each of us underestimates the number of stupid
   individuals in circulation.
 * The probability that a given person is stupid is independent of any other
   characteristic possessed by that person.
 * A person is stupid if they cause damage to another person or group of people
   without experiencing personal gain, or even worse causing damage to themselves
   in the process.
 * Non-stupid people always underestimate the harmful potential of stupid people;
   they constantly forget that at any time anywhere, and in any circumstance,
   dealing with or associating themselves with stupid individuals invariably
   constitutes a costly error.
 * A stupid person is the most dangerous type of person there is.
 - Carlo Maria Cipolla

"Never underestimate the power of stupid people in large groups." - George Carlin

"Think of how stupid the average person is, and realize half
 of them are stupider than that." - George Carlin