If fifty million people say a foolish thing, it is still a foolish thing.

[Si 50 millions de personnes disent une bêtise, c’est quand même une bêtise.]

Anatole France (1844-1924) French poet, journalist, novelist, Nobel Laureate [pseud. of Jaques-Anatole-François Thibault]

(Spurious)

Sometimes also misattributed to Bertrand Russell. The closest to this specific quotation comes from W. Somerset Maugham. More information about this quotation, including the source of this misattribution and an analogous phrase France did use: If Fifty Million People Say a Foolish Thing, It Is Still a Foolish Thing – Quote Investigator.