In the film Manufacturing Consent, Chomsky states on camera that he wrote the
"essay" as an "essay", not a "preface"; but he did know of the publisher's intent, because he also admits that at the last minute he did ask them not to use it, because he thought no one at that point would understand what he was really trying to say (about freedom of speech). They went ahead, anyway. He further states that making that request to for them not to use it was the mistake he made (it got into the press). .And he repeatedly maintains that he supported Faurisson's right to speak his ideas, but not Faurrison himself, and that there is a difference...all this is in an entire segment that deals with this incident.
I myself think A) he made a big ol' mistake, B) he's too stubborn to ever back down, C) anybody who seriously thinks Noam Chomsky really supports the ideas of Holocaust deniers is very confused, and D) while it's regrettable that what he did made Mr Lawrence's job in Mississippi tougher, I think you have to weigh that against the man's positive contributions to the left for all these years...
just a thought