… is from pages 11-12 of the 1969 Arlington House edition of Ludwig von Mises’s 1944 Yale University Press book, Omnipotent Government: The Rise of the Total State and Total War  (available free-of-charge on-line here ):
Every doctrine that has recourse to the police power or to other methods of violence or threat for its protection reveals its inner weakness.
DBx: Who can doubt the truth of this observation? Any person or group who threatens with physical violence those who offer challenging words is a person or group whose ideas and ideals are not worth defending. This fact is so regardless of the brilliance of the superficial gleam emitted by those ideas and ideals.