"You can kill a man, but you cannot kill an idea.” ~ Italian independence movement of 1844.
“You cannot kill an idea” ~ about Christianity in 1882.
“You can kill a man, but you can’t kill an idea” ~ NAACP posters in 1964 in association with slain civil rights leader Medgar Evers (1925-1963).
“Ideas are bulletproof” ("You can kill a man, but you cannot kill an idea") ~ Alan Moore, 1989
PZ Myers, "an American biology professor at the University of Minnesota Morris (UMM) and the author of the popular science blog Pharyngula. A self-avowed "godless liberal" and outspoken atheist, he is a vocal skeptic of all forms of religion, superstition, supernaturalism, spirituality and pseudoscience.
A corollary to the above:
When any government, or any church for that matter, undertakes to say to its subjects, "This you may not read, this you must not see, this you are forbidden to know," the end result is tyranny and oppression, no matter how holy the motives. Mighty little force is needed to control a man whose mind has been hoodwinked; contrariwise, no amount of force can control a free man, a man whose mind is free. No, not the rack, not fission bombs, not anything — you can't conquer a free man; the most you can do is kill him.
-- Robert A. Heinlein
A great comment! Your man, Heinlein, comes through again.