It takes all natons to keep the peace, but it only takes one to start a war.
~ Robert A. Heinlein
It takes all people to be sensible, but it only takes one lunatic to destroy truth. OK, not as good a quote but I'm thinking of a NY Times article "Where Facts Were No Match for Fear: Civic boosters in central Montana hoped for some federal money to promote tourism. A disinformation campaign got in the way.". One person with no facts destroyed a long-planned project that had no drawbacks and would have helped the area. Repeat lies enough & people will begin to wonder & then decide it's safer not to proceed when there are still "questions."