Star Trek: The Next Generation
S4E21 - The Drumhead
"With the first link, the chain is forged. The first speech censured, the first thought forbidden, the first freedom denied, chains us all irrevocably."
Captain Jean Luc Picard quoting Judge Aaron Satie
Later, he continues:
"Mr. Worf, villains who twirl their moustaches are easy to spot. Those who clothe themselves in good deeds are well camouflaged.
...
But she, or someone like her, will always be with us. Waiting for the right climate in which to flourish. Spreading fear in the name of righteousness. Vigilance, Mr. Worf. That is the price we have to continually pay."