Here are some sayings about fanatics and fanatacism. Feel free to add quotes, whiticisms or zingers.
SS
FANATICS
"Wisdom becomes nonsense in the mouth of a fanatic."
(Otto Schuwdrmer)
"A fanatic is one who can't change his mind and won't change the subject."
(Winston S. Churchill, 1874-1965)
"A fanatic is a man who consciously over compensates a secret doubt."
(Aldous Huxley)
"A fanatic is a man that does what he thinks the Lord would do if He knew the facts of the case."
(Finley Peter Dunne)
"The fanatic is incorruptible: if he kills for an idea, he can just as well get himself killed for one; in either case, tyrant or martyr, he is a monster."
(E. M. Cioran)
FANATICISM
"In the history of mankind, fanaticism has caused more harm than vice."
(Louis Kronenberger)
"Fanaticism consists in redoubling your effort when you have forgotten your aim."
(George Santayana)