Intelligence is the capacity to receive, decode and transmit information efficiently. Stupidity is blockage of this process at any point. Bigotry, ideologies etc. block the ability to receive; robotic reality-tunnels block the ability to decode or integrate new signals; censorship blocks transmission.
Also a great quote from Alan Watts:
Inability to accept the mystic experience is more than an intellectual handicap. Lack of awareness of the basic unity of organism and environment is a serious and dangerous hallucination. For in a civilization equipped with immense technological power, the sense of alienation between man and nature leads to the use of technology in a hostile spirit—to the “conquest” of nature instead of intelligent co-operation with nature.
Note that there’s also a Bill Hicks video page.