A communist caring about "his" democracy? That's new. Wasn't he pro-Pol Pot?
When the truth came out, his opinion did not need to change. Rather, he would point out that he was right in his position with the "information available at the time".
http://www.abc.net.au/news/2011-07-01/brull---the-boring-tru...
That whole controversy centers around him pointing out that a book by a guy called Ponchaud which was being used as a pretext to try and go to war was full of errors.
It was full of errors.
For an outline of the points brought forth, you may read this: http://www.paulbogdanor.com/chomsky/wma.html
What the article you linked refers to as "full of errors" was in fact a review of the book by Jean Lacouture.