There's a difference between saying something and trying to influence others. There should be some limitation on what one is allowed to do to change what others think I believe. Otherwise false advertising, child porn, halocaust denial, personal deflammation, etc. would all be legal. The democratic process should help in setting those limits I think.
I don't believe freedom of speech is necessary for democracy, and democracy is not necessary for freedom of speech. The two things just somehow ended up lumped together mostly for historical reasons I think.