didn't say it, it was actually a biographer:
The men who had hated [the book], and had not particularly loved Helvétius, flocked round him now. Voltaire forgave him all injuries, intentional or unintentional. 'What a fuss about an omelette!' he had exclaimed when he heard of the burning. How abominably unjust to persecute a man for such an airy trifle as that! 'I disapprove of what you say, but I will defend to the death your right to say it,' was his attitude now.It was by Evelyn Beatrice Hall, who used the pseudonym S. G. Tallentyre. Apparently a lot of famous quotes weren't really said by the supposed speakers - like "Damn the torpedoes, full speed ahead!" by David Farragut (as in Farraguts North and West). Pretty interesting.